Neurotoxicity from immune-checkpoint inhibition in the treatment of melanoma: a single centre experience and review of the literature.

Background: Treatment with immune checkpoint inhibitors (ICPi) has greatly improved survival for patients with advanced melanoma in recent years. Anti-CTLA-4 and anti-PD1 antibodies have been approved following large Phase III trials. Immune-related neurological toxicity of varying severity has been reported in the literature. The cumulative incidence of neurotoxicity among ipilimumab, nivolumab and pembrolizumab is reported as <1% in published clinical trials. We aimed to identify the incidence of neurotoxicity in our institution across anti-CTLA4 and anti-PD-1 antibodies, including the combination of ipilimumab with nivolumab. We also review the existing literature and propose an investigation and management algorithm. Methods: All patients with advanced melanoma treated with ipilimumab, nivolumab, pembrolizumab or the combination of ipilimumab and nivolumab (ipi + nivo), managed at the Royal Marsden Hospital between September 2010 and December 2015, including patients on (published) clinical trials were included. Medical records for each patient were reviewed and information on neurotoxicity recorded. A systematic search strategy was performed to collate existing reports of neurological toxicity. Results: In total, 413 immunotherapy treatment episodes in 352 patients were included, with median follow-up of 26.7 months. Ten cases of neurotoxicity were recorded, affecting 2.8% of patients overall, ranging from grade 1 to 4, affecting both central and peripheral nervous systems. A rate of 14% was noted with ipi + nivo. Three of five patients commenced on corticosteroids responded to these. Six patients had made a full recovery at the time of reporting. A favorable radiological response was found in 7 of the 10 cases. Unusual presentations are described in detail. Conclusions: Neurological toxicity is not uncommon, and may be more frequent in patients treated with combination ipi + nivo. Patterns of presentation and response to treatment are varied. A prompt and considered approach is required to optimize outcomes in this group of patients.

[Peripartum cardiomyopathy: clinical key to diagnosis]. / Miocardiopatía periparto: claves clínicas para su sospecha.

Peripartum cardiomyopathy (PPCM) is an idiopathic cardiomyopathy that is caused by heart failure secondary to a dysfunction of the left ventricle at the end of pregnancy or in the first months following childbirth. The diagnosis is performed by electrocardiogram, radiography of the thorax and increase of natriuretic peptides. Bedside radiography can contribute with data that help early diagnosis. Treatment is carried out following clinical guidelines for heart failure, taking into account potentially teratogenic drugs. The importance of this pathology lies in that it affects women at a fertile age and is potentially mortal, which is why there must be a high index of suspicion for its diagnosis and a differential diagnosis with other entities. In this clinical note we present a series of cases of PPCM with the goal of reviewing the diagnosis and treatment of this entity.

Spin crossover in a catenane supramolecular system.

The compound [Fe(tvp)(2)(NCS)(2)] . CH(3)OH, where tvp is 1,2-di-(4-pyridyl)-ethylene, has been synthesized and characterized by x-ray single-crystal diffraction. It consists of two perpendicular, two-dimensional networks organized in parallel stacks of sheets made up of edge-shared [Fe(II)](4) rhombuses. The fully interlocked networks define large square channels in the [001] direction. Variable-temperature magnetic susceptibility measurements and Mössbauer studies reveal that this compound shows low-spin to high-spin crossover behavior in the temperature range from 100 to 250 kelvin. The combined structural and magnetic characterization of this kind of compound is fundamental for the interpretation of the mechanism leading to the spin crossover, which is important in the development of electronic devices such as molecular switches.

The influence of pseudohalide ligands on the SIM behaviour of four-coordinate benzylimidazole-containing cobalt(ii) complexes.

Three, mononuclear complexes of the formula [Co(bmim)2(SCN)2] (1), [Co(bmim)2(NCO)2] (2) and [Co(bmim)2(N3)2] (3) [bmim = 1-benzyl-2-methylimidazole] were prepared and structurally analyzed by single-crystal X-ray crystallography. The cobalt(ii) ions in 1-3 are tetrahedrally coordinated with two bmim molecules and two pseudohalide anions. The angular distortion parameter δ was calculated and the SHAPE program (based on the CShM concept) was used for 1-3 to estimate the angular distortion from an ideal tetrahedron. The molecules of 1-3 are effectively separated, and the values of the shortest distance of cobalt-cobalt are 8.442(6) and 6.774(8) Å for 1, 10.349(8) and 10.716(8) Å for 2 and 6.778(1) and 9.232(1) Å for 3. Direct current (dc) magnetic susceptibility measurements on the crushed crystals of 1-3 were carried out in the temperature range 1.9-295 K. The variable-temperature magnetic data of 1-3 mainly obey the zero-field splitting effect (D) of the 4A2 ground term of the tetrahedral cobalt(ii) complexes (2D being the energy gap between the |±1/2 and |±3/2 levels of the spin). The analysis of their magnetic data through the Hamiltonian H = D[S2z - S(S + 1)/3] + E(Sx2 - Sy2) + gßHS led to the following best-fit parameters: g = 2.29, D = -7.5 cm-1 and E/D = 0.106 (1), g = 2.28, D = + 6.3 cm-1 and E/D = 0.007 (2) and g = 2.36, D = + 6.7 cm-1 and E/D = 0.090 (3). The signs of D for 1-3 were confirmed by Q-band EPR spectra on powdered samples in the temperature range 4.0-20 K. Field-induced SIM behaviour was observed for 1-3 below 4.0 K, and the frequency-dependent maxima of χ''M were observed for 1 and only incipient signals of χ''M occurred for 2 and 3. The values of the exponential factor (τ0) and activation energy (Ea) for 1-3 which were obtained from the Arrhenius plot suggest a single relaxation process characteristic of an Orbach mechanism.

Reversible solvatomagnetic switching in a single-ion magnet from an entatic state.

A vast impact on molecular nanoscience can be achieved using simple transition metal complexes as dynamic chemical systems to perform specific and selective tasks under the control of an external stimulus that switches "ON" and "OFF" their electronic properties. While the interest in single-ion magnets (SIMs) lies in their potential applications in information storage and quantum computing, the switching of their slow magnetic relaxation associated with host-guest processes is insufficiently explored. Herein, we report a unique example of a mononuclear cobalt(ii) complex in which geometrical constraints are the cause of easy and reversible water coordination and its release. As a result, a reversible and selective colour and SIM behaviour switch occurs between a "slow-relaxing" deep red anhydrous material (compound 1) and its "fast-relaxing" orange hydrated form (compound 2). The combination of this optical and magnetic switching in this new class of vapochromic and thermochromic SIMs offers fascinating possibilities for designing multifunctional molecular materials.

An {Fe60} tetrahedral cage: building nanoscopic molecular assemblies through cyanometallate and alkoxo linkers.

A nanoscopic {Fe60} coordination cage (approximately 3 nm) was prepared by the self assembly of a partially blocked tricyanidoferrate(iii) complex and tris(alkoxo)-based iron(iii) coordination motifs. This cage is a rare example of a mixed cyanido/alkoxo-bridged high nuclearity complex and it exemplifies the great potential of this new synthetic route to generate uncommon molecular architectures using cyanometallates as metalloligands versus alkoxo-based polynuclear entities.

Synthesis, crystal structure and magnetic properties of H2tppz[ReCl6] and [Cu(bpzm)2(µ-Cl)ReCl3(µ-ox)Cu(bpzm)2(µ-ox)ReCl3(µ-Cl)]n.

Two new Re(iv) compounds of formulae H2tppz[ReCl6] (1) and [Cu(bpzm)2(µ-Cl)ReCl3(µ-ox)Cu(bpzm)2(µ-ox)ReCl3(µ-Cl)]n (2) [tppz = 2,3,5,6-tetrakis(2-pyridyl)pyrazine and bpzm = bis(pyrazolyl-1-yl)methane] have been prepared and their crystal structures determined by X-ray diffraction on single crystals. Compound 1 is a mononuclear species whose structure consists of octahedral hexachlororhenate(iv) anions and diprotonated H2tppz(2+) cations which are arranged in the unit cell as alternating anionic and cationic layers, held together by electrostatic forces. The structure of 2 is made up of alternating [Cu(1)(bpzm)2](2+) and [(ox)ReCl3(µ-Cl)Cu(2)(bpzm)2(µ-Cl)ReCl3(ox)](2-) entities interlinked by oxalate bridges to afford a neutral heterobimetallic chain. The oxalate group adopts the didentate (at Re)/monodentate (at Cu) bridging mode. The magnetic behavior of 1 and 2 has been investigated over the temperature range 1.9-295 K. 1 is a magnetically diluted Re(iv) complex, the relatively large value of the zero-field splitting of the ground level [D = -15.8(2) cm(-1)] accounting for the variation of χMT in the low temperature range. Weak intrachain ferromagnetic interactions between Re(iv) and Cu(ii) through oxalate (J1 = +0.15 cm(-1)) and single chloro (J2 = +4.9 cm(-1)) bridges occur in 2 which are obscured by the large zero-field splitting of the Re(iv) ion (DRe = 42 cm(-1)). In addition, interchain antiferromagnetic interactions are also involved in 2 which are responsible for the metamagnetic behavior observed, the value of the critical dc magnetic field (Hc) being 20 kOe.

Ferromagnetic Coupling through Spin Polarization in a Dinuclear Copper(II) Metallacyclophane.

First organic radicals, now metal complexes: A successful extension to metal complexes of a well-known organic radical approach to ferromagnetism is exemplified by the triplet ground-state molecule containing two Cu(II) centers connected by a double m-phenylenediamide skeleton of the cyclophane type shown in the scheme.

[Relationship between echocardiographic measurement of left atrial size and the incidence of systemic embolism in mitral stenosis]. / Relación entre el tamaño ecocardiográfico auricular izquierdo con la incidencia de embolia sistémica en la estenosis mitral.

In order to correlate left atrial diameter (LAD) with the prevalence of systemic embolism (SE) in mitral stenosis (MS), we assessed LAD by M mode tracings in 51 patients with SE and in 50 patients with MS without ES as control group (C). Mean age was similar in both groups (SE 47.3 +/- 12 vs C 46.8 +/- 14 years; p NS) (mean +/- SD). Functional class, cardiothoracic ratio and association of other valvular lesions were similar in both groups. Atrial fibrillation (AF) was more frequent in SE group (n = 39) than in C group (n = 20) (p less than 0.01). LAD in SE patients ranged from 2.9 to 9 cm (5.2 +/- 1) whereas in C patients range was from 2.8 to 7.5 (4.6 +/- 1) (p less than 0.01). Nevertheless, LAD in patients with AF was rather similar in both groups (SE 5.3 +/- 1.1 vs C 5.3 +/- 1; p NS). Our results suggest that LAD is not a good predictive parameter for SE in MS. The main risk factor for SE was the existence of AF. Echocardiographic LAD is not a useful parameter to prescribe chronic oral anticoagulation as prophylaxis for SE in patients with MS.

[Effect of 3 hypertensive++ agents on ventricular geometry and function]. / Efecto de tres antihipertensivos sobre la geometría y función ventriculares.

BACKGROUND: To assess the prevalence of left ventricular hypertrophy in hypertensive patients referred to an outpatient cardiology unit, and to assess its evolution under antihypertensive treatment. METHODS: One hundred and seven mild to moderate hypertensive patients were randomized to receive either xipamide, verapamil or atenolol. Cross-sectional echocardiography was performed in order to assess left ventricular mass and function. RESULTS: Mean age was 56 years, with a 4:1 female/male ratio. Mean follow-up was 120 days. Left ventricular hypertrophy was very common (65%) and decreased to 54% under antihypertensive treatment. Left ventricular mass decreased from 134.3 g/m2 to 118.1 g/m2 (p < 0.001). Concentric hypertrophy was the most common geometric pattern (42%), decreasing to 30% with treatment. Xipamide decreased ventricular mass by decreasing left ventricular diameters, while verapamil and atenolol decreased left ventricular thickness, mainly in septal wall. Systolic function was not modified during the treatment period. Diastolic function was not modified by xipamide and verapamil, and improved with atenolol. CONCLUSIONS: Left ventricular hypertrophy is very frequent when determined by echocardiography and all three drugs produced regression of left ventricular hypertrophy in a different way with respect to left ventricle geometry, an effect which could have potential therapeutic implications.

Use of mTOR inhibitors in chronic heart transplant recipients with renal failure: calcineurin-inhibitors conversion or minimization?

BACKGROUND: In the last decade, mTOR inhibitors (mTOR-is) have become the cornerstone of the calcineurin inhibitor (CNI)-reduced/free regimens aimed to the preservation of post-transplant renal function. We compared utility and safety of the total replacement of calcineurin inhibitors with a mTOR-i with a strategy based on calcineurin inhibitor minimization and concomitant use of m-TOR-i. METHODS: In a retrospective multi-center cohort of 394 maintenance cardiac recipients with renal failure (GFR<60 mL/min/1.73 m(2)), we compared 235 patients in whom CNI was replaced with a mTOR-i (sirolimus or everolimus) with 159 patients in whom mTOR-is were used to minimize CNIs. A propensity score analysis was carried out to balance between group differences. RESULTS: Overall, after a median time of 2 years from mTOR-i initiation, between group differences for the evolution of renal function were not observed. In a multivariate adjusted model, improvement of renal function was limited to patients with mTOR-i usage within 5years after transplantation, particularly with the conversion strategy, and in those patients who could maintain mTOR-i therapy. Significant differences between strategies were not found for mortality, infection and mTOR-i withdrawal due to drug-related adverse events. However, conversion group tended to have a higher acute rejection incidence than the minimization group (p=0.07). CONCLUSION: In terms of renal benefits, our results support an earlier use of mTOR-is, irrespective of the strategy. The selection of either a conversion or a CNI minimization protocol should be based on the clinical characteristics of the patients, particularly their rejection risk.

Synthesis, crystal structures and magnetic properties of tricyanomethanide-containing copper(II) complexes.

The preparation, crystal structures and magnetic properties of the copper(II) complexes of formula [Cu(pyim)(tcm)(2)](n) (1), [Cu(bpy)(tcm)(2)](n) (2), [Cu(4)(bpz)(4)(tcm)(8)] (3), {[Cu(terpy)(tcm)].tcm}(n) (4) and {[Cu(2)(tppz)(tcm)(4)].3/2H(2)O}(n) (5) [pyim = 2-(2-pyridyl)imidazole, tcm = tricyanomethanide, bpy = 2,2'-bipyridine, bpz = 2,2'-bipyrazine, terpy = 2,2':6',2''-terpyridine and tppz = 2,3,5,6-tetrakis(2-pyridyl)pyrazine] are reported. Complexes, 1, 2 and 4 are uniform copper(II) chains with single- (1 and 4) and double-(2) micro-1,5-tcm bridges with values of the intrachain copper-copper separation of 7.489(1) (1), 7.520(1) and 7.758(1) (2) and 7.469(1) A (4). Each copper atom in 1, 2 and 4 is five-coordinate with bidentate pyim (1)/bpy (2) and tridentate terpy (4) ligands and nitrile-nitrogen atoms from bridging (1,2 and 4) and terminal (1) tcm groups building a distorted square pyramidal surrounding. The structure of 3 is made up of neutral centrosymmetric rectangles of (2,2'-bipyrazine)copper(II) units at the corners, the edges being built by single- and double-micro-1,5-tcm bridges with copper-copper separations of 7.969(1) and 7.270(1) A, respectively. Five- and six-coordinated copper atoms with distorted square pyramidal and elongated octahedral environments occur in . Compound 5 is a neutral copper(II) chain with regular alternating bis-tridentate tppz and double micro-1,5-tcm bridges, the intrachain copper-copper distances being 6.549(7) and 7.668(1) A, respectively. The two crystallographically independent copper atoms in 5 have an elongated octahedral geometry with three tppz nitrogen atoms and a nitrile-nitrogen atom from a bridging tcm group in the equatorial positions, and two nitrile nitrogen atoms from a terminal and a bridging tcm ligand occupying the axial sites. The investigation of the magnetic properies of 1-5 in the temperature range 1.9-295 K has shown the occurrence of weak ferro- [J = +0.11(1) cm(-1) (2)] and antiferromagnetic interactions [J = -0.093(1) (1), -0.083(1) (4), -0.04(1) and 1.21(1) cm(-1) (3)] across the micro-1,5-tcm bridges and intermediate antiferromagnetic coupling [-J = 37.4(1) cm(-1) (5)] through bis-tridentate tppz. The values of the magnetic interactions are analyzed through simple orbital symmetry considerations and compared with those previously reported for related systems.

Syntheses, crystal structures, and magnetic properties of one-dimensional oxalato-bridged Co(II), Ni(II), and Cu(II) complexes with n-aminopyridine (n = 2-4) as terminal ligand.

The reaction of M(ox) x 2H(2)O (M = Co(II), Ni(II)) or K(2)(Cu(ox)(2)) x 2H(2)O (ox = oxalate dianion) with n-ampy (n = 2, 3, 4; n-ampy = n-aminopyridine) and potassium oxalate monohydrate yields one-dimensional oxalato-bridged metal(II) complexes which have been characterized by FT-IR spectroscopy, variable-temperature magnetic measurements, and X-ray diffraction methods. The complexes M(mu-ox)(2-ampy)(2) (M = Co (1), Ni (2), Cu (3)) are isomorphous and crystallize in the monoclinic space group C2/c (No. 15), Z = 4, with unit cell parameters for 1 of a = 13.885(2) A, b = 11.010(2) A, c = 8.755(1) A, and beta = 94.21(2) degrees. The compounds M(mu-ox)(3-ampy)(2).1.5H(2)O (M = Co (4), Ni (5), Cu (6)) are also isomorphous and crystallize in the orthorhombic space group Pcnn (No. 52), Z = 8, with unit cell parameters for 6 of a = 12.387(1), b = 12.935(3), and c = 18.632(2) A. Compound Co(mu-ox)(4-ampy)(2) (7) crystallizes in the space group C2/c (No. 15), Z = 4, with unit cell parameters of a = 16.478(3) A, b = 5.484(1) A, c = 16.592(2) A, and beta = 117.76(1) degrees. Complexes M(mu-ox)(4-ampy)(2) (M = Ni (8), Cu (9)) crystallize in the orthorhombic space group Fddd (No. 70), Z = 8, with unit cell parameters for 8 of a = 5.342(1), b = 17.078(3), and c = 29.469(4) A. All compounds are comprised of one-dimensional chains in which M(n-ampy)(2)(2+) units are sequentially bridged by bis-bidentate oxalato ligands with M.M intrachain distances in the range of 5.34-5.66 A. In all cases, the metal atoms are six-coordinated to four oxygen atoms, belonging to two bridging oxalato ligands, and the endo-cyclic nitrogen atoms, from two n-ampy ligands, building distorted octahedral surroundings. The aromatic bases are bound to the metal atom in cis (1-6) or trans (7-9) positions. Magnetic susceptibility measurements in the temperature range of 2-300 K show the occurrence of antiferromagnetic intrachain interactions except for the compound 3 in which a weak ferromagnetic coupling is observed. Compound 7 shows spontaneous magnetization below 8 K, which corresponds to the presence of spin canted antiferromagnetism.

Magnetically isolated Cu(II)Gd(III) pairs in the series [Cu(acacen)Gd(pta)(3)], [Cu(acacen)Gd(hfa)(3)], [Cu(salen)Gd(pta)(3)], and [Cu(salen)Gd(hfa)(3)], [acacen = N,N'-ethylenebis(acetylacetoniminate(-)), salen = N,N'-ethylenebis(salicylideniminate(-)), hfa = 1,1,1,5,5,5-hexafluoropentane-2,4-dionate(-), pta = 1,1,1-trifluoro-5,5-dimethylhexane-2,4-dionate(-)].

[Cu(salen)Gd(pta)(3)] (1), [Cu(acacen)Gd(pta)(3)] (2), and [Cu(acacen)Gd(hfa)(3)] (3) are three heterobimetallic [Cu(II)Gd(III)] complexes of general formula [Cu(SB)Gd(beta-dik)(3)], in which a N,N',O,O' Schiff base (SB) ligand [acacen = N,N'-ethylenebis(acetylacetoniminate(-)), salen = N,N'-ethylenebis(salicylideneiminate(-))] tetracoordinates Cu(II) and chelates Gd(III) as a tris(beta-diketonate) complex [hfa = 1,1,1,5,5,5-hexafluoropentane-2,4-dionate(-); pta = 1,1,1-trifluoro-5,5-dimethylhexane-2,4-dionate(-)]. They crystallize as a triclinic structure (space group P). The cell parameters are a = 9.8616(10) A, b = 12.1976(13) A, c = 18.4187(22) A, alpha = 90.671(14) degrees, beta = 100.588(13) degrees, gamma = 103.684(12) degrees, V = 2113 A(3), and Z = 2 for 1; a = 9.7560(11) A, b = 12.2924(13) A, c = 18.9368(22) A, alpha = 88.449(14) degrees, beta = 87.269(14) degrees, gamma = 67.629(12) degrees, V = 2098 A(3), and Z = 2 for 2; and a = 12.5726(15) A, b = 15.5985(18) A, c = 18.3724(21) A, alpha = 85.963(13) degrees, beta = 85.411(14) degrees, gamma = 80.766(14) degrees, V = 3539 A(3), and Z = 4 for 3. The Cu(O,O')Gd bridging cores show folding angles about O,O' in the range 139 degrees -147 degrees and intramolecular Cu small middle dot small middle dot small middle dotGd distances of about 3.3 A. In the solid state, the molecules form centrosymmetric pseudodimers [Cu(SB)Gd(beta-dik)(3)](2), through the overlap of the Cu(SB) entities. Resulting intradimer Cu...Cu distances are 5.941(1) A for 1, 4.831(1) A for 2, and 4.511(1) and 3.868(1) A for 3 which comprises two symmetrically independent dimers. The temperature dependence of complexes 1-3 was investigated in the range 1.8-300 K and revealed weak ferromagnetic interactions. Results are discussed in light of the structural features and of available magnetostructural data for other heterobimetallic [Cu(II)Gd(III)] complexes, including [Cu(salen)Gd(hfa)(3)] (4) (Ramade, I.; Kahn, O.; Jeannin, Y.; Robert, F. Inorg. Chem. 1997, 36, 930-936).

Ferromagnetism in malonato-bridged copper(II) complexes. Synthesis, crystal structures, and magnetic properties of [[Cu(H2O)3][Cu(mal)2(H2O)]]n and [[Cu(H2O)4]2[Cu(mal)2(H2O)]][Cu(mal)2(H2O)2][[Cu(H2O)4][Cu(mal)2(H2O)2][(H2mal = malonic acid).

Three malonato-bridged copper(II) complexes of the formulas [[Cu(H2O)3][Cu(C3H2O4)2(H2O)]]n (1), [[Cu(H2O)4]2[Cu(C3H2O4)2(H2O)]] [Cu(C3H2O4)2(H2O)2][[Cu(H2O)4][Cu(C3H2O4)2(H2O)2]] (2), and [Cu(H2O)4][Cu(C3H2O4)2(H2O)2] (3) (C3H2O4 = malonate dianion) have been prepared, and the structures of the two former have been solved by X-ray diffraction methods. The structure of compound 3 was already known. Complex 1 crystallizes in the orthorhombic space group Pcab, Z = 8, with unit cell parameters of a = 10.339(1) A, b = 13.222(2) A, and c = 17.394(4) A. Complex 2 crystallizes in the monoclinic space group P2/c, Z = 4, with unit cell parameters of a = 21.100(4) A, b = 21.088(4) A, c = 14.007(2) A, and beta = 115.93(2) degrees. Complex 1 is a chain compound with a regular alternation of aquabis(malonato)copper(II) and triaquacopper(II) units developing along the z axis. The aquabis(malonato)copper(II) unit acts as a bridging ligand through two slightly different trans-carboxylato groups exhibiting an anti-syn coordination mode. The four carboxylate oxygens, in the basal plane, and the one water molecule, in the apical position, describe a distorted square pyramid around Cu1, whereas the same metal surroundings are observed around Cu2 but with three water molecules and one carboxylate oxygen building the equatorial plane and a carboxylate oxygen from another malonato filling the apical site. Complex 2 is made up of discrete mono-, di-, and trinuclear copper(II) complexes of the formulas [Cu(C3H2O4)2(H2O)2]2-, [[Cu(H2O)4] [Cu(C3H2O4)2(H2O)2]], and [[Cu(H2O)4]2[Cu(C3H2O4)2(H2O)]]2+, respectively, which coexist in a single crystal. The copper environment in the mononuclear unit is that of an elongated octahedron with four carboxylate oxygens building the equatorial plane and two water molecules assuming the axial positions. The neutral dinuclear unit contains two types of copper atoms, one that is six-coordinated, as in the mononuclear entity, and another that is distorted square pyramidal with four water molecules building the basal plane and a carboxylate oxygen in the apical position. The overall structure of this dinuclear entity is nearly identical to that of compound 3. Finally, the cationic trimer consists of an aquabis(malonato)copper(II) complex that acts as a bismonodentate ligand through two cis-carboxylato groups (anti-syn coordination mode) toward two tetraaqua-copper(II) terminal units. The environment of the copper atoms is distorted square pyramidal with four carboxylate oxygens (four water molecules) building the basal plane of the central (terminal) copper atom and a water molecule (a carboxylate oxygen) filling the axial position. The magnetic properties of 1-3 have been investigated in the temperature range 1.9-290 K. Overall, ferromagnetic behavior is observed in the three cases: two weak, alternating intrachain ferromagnetic interactions (J = 3.0 cm-1 and alpha J = 1.9 cm-1 with H = -J sigma i[S2i.S2i-1 + alpha S2i.S2i+1]) occur in 1, whereas the magnetic behavior of 2 is the sum of a magnetically isolated spin doublet and ferromagnetically coupled di- (J3 = 1.8 cm-1 from the magnetic study of the model complex 3) and trinuclear (J = 1.2 cm-1 with H = -J (S1.S2 + S1.S3) copper(II) units. The exchange pathway that accounts for the ferromagnetic coupling, through an anti-syn carboxylato bridge, is discussed in the light of the available magneto-structural data.

[Fe(Phen)(CN)4]-: a versatile building block for the design of heterometallic systems. Crystal structures and magnetic properties of PPh4[Fe(Phen)(CN)4]*2H2O and [[Fe(Phen)(CN)4]2M(H2O)2]*4H2O [Phen = 1,10-phenanthroline; M = Mn(II) and Zn(II)].

The mononuclear PPh4[Fe(phen)(CN)4]*2H2O (1) complex and the cyanide-bridged bimetallic [[Fe(phen)(CN)4]2M(H2O)2]*4H2O compounds [M = Mn(II) (2) and Zn(II) (3); phen = 1,10-phenanthroline; PPh4 = tetraphenylphosphonium cation] have been synthesized and structurally and magnetically characterized. Complex 1 crystallizes in the monoclinic system, space group P2(1)/c, with a = 9.364(4) A, b = 27.472(5) A, c = 14.301(3) A, beta = 97.68(2) degrees, and Z = 4. Complexes 2 and 3 are isostructural and they crystallize in the monoclinic system, space group P2(1)/n, with a = 7.5292(4) A, b = 15.6000(10) A, c = 15.4081(9) A, beta = 93.552(2) degrees, and Z = 2 for 2 and a = 7.440(1) A, b = 15.569(3) A, c = 15.344(6) A, beta = 93.63(2) degrees, and Z = 2 for 3. The structure of complex 1 is made up of mononuclear [Fe(phen)(CN)4]- anions, tetraphenyphosphonium cations, and water molecules of crystallization. The iron(III) is hexacoordinate with two nitrogen atoms of a chelating phen (2.018(6) and 2.021(6) A for Fe-N) and four carbon atoms of four terminal cyanide groups (Fe-C bond lengths varying in the range 1.906(8)-1.95(1) A) building a distorted octahedron around the metal atom. The structure of complexes 2 and 3 consists of neutral double zigzag chains of formula [[Fe(phen)(CN)4]2M(H2O)2] and crystallization water molecules. The [Fe(phen)(CN)4]- entity of 1 is present in 2 and 3 acting as a bridging ligand toward M(H2O)2 units [M = Mn(II) (2) and Zn(II) (3)] through two cyanide groups in cis positions, the other two cyanide remaining terminal. Two water molecules in trans positions and four cyanide-nitrogen atoms from four [Fe(phen)(CN)4]- units build a distorted octahedral surrounding Mn(II) (2) and Zn(II) (3). The M-O bond lengths are 2.185(3) (2) and 2.105(3) A (3), whereas the M-N bond distances vary in the ranges 2.210(3)-2.258(3) A (2) and 2.112(3)-2.186(3) A (3). The structure of the [Fe(phen)(CN)4]- complex ligand in 2 and 3 is as in 1. The shorter intrachain Fe-M distances through bridging cyano are 5.245(5) and 5.208(5) A in 2 and 5.187(1) and 5.132(1) A in 3. The magnetic properties of 1-3 have been investigated in the temperature range 2.0-300 K. Complex 1 is a low-spin iron(III) complex with an appreciable orbital contribution. The magnetic properties of 3 correspond to the sum of two magnetically isolated spin triplets, the magnetic coupling between the low-spin iron(III) centers through the -CN-Zn-NC- bridging skeleton (iron-iron separation larger than 10.2 A) being negligible. More interestingly, 2 exhibits one-dimensional ferrimagnetic behavior due to the noncompensation of the local interacting spins (S(Mn) = 5/2 and S(Fe) = 1/2) which interact antiferromagnetically through bridging cyano groups. A comparison between the magnetic properties of the isostructural compounds 2 and 3 allow us to check the antiferromagnetic coupling in 2.

Syntheses, crystal structures, and magnetic properties of the oxalato-bridged mixed-valence complexes (FeII(bpm)3]2[FeIII2(ox)5].8H2O and FeII(bpm)3Na(H2O)2Fe(ox)(3).4H2O (bpm = 2,2'-bipyrimidine).

The preparation and crystal structures of two oxalato-bridged FeII-FeIII mixed-valence compounds, [FeII(bpm)3]2[FeIII2(ox)5].8H2O (1) and FeII(bpm)3Na(H2O)2FeIII(ox)(3).4H2O (2) (bpm = 2,2'-bipyrimidine; ox = oxalate dianion) are reported here. Complex 1 crystallizes in the triclinic system, space group P1, with a = 10.998(2) A, b = 13.073(3) A, c = 13.308(3) A, alpha = 101.95(2) degrees, beta = 109.20(2) degrees, gamma = 99.89(2) degrees, and Z = 1. Complex 2 crystallizes in the monoclinic system, space group P2(1)/c, with a = 12.609(2) A, b = 19.670(5) A, c = 15.843(3) A, beta = 99.46(1) degrees, and Z = 4. The structure of complex 1 consists of centrosymmetric oxalato-bridged dinuclear high-spin iron(III) [Fe2(ox)5]2- anions, tris-chelated low-spin iron(II) [Fe(bpm)3]2+ cations, and lattice water molecules. The iron atoms are hexacoordinated: six oxygen atoms (iron(III)) from two bidentate and one bisbidentate oxalato ligands and six nitrogen atoms (iron(II)) from three bidentate bpm groups. The Fe(III)-O(ox) and Fe(II)-N(bpm) bond distances vary in the ranges 1.967(3)-2.099(3) and 1.967(4)-1.995(3) A, respectively. The iron(III)-iron(III) separation across the bridging oxalato is 5.449(2) A, whereas the shortest intermolecular iron(III)-iron(II) distance is 6.841(2) A. The structure of complex 2 consists of neutral heterotrinuclear Fe(bpm)2Na(H2O)2Fe(ox)3 units and water molecules of crystallization. The tris-chelated low-spin iron(II) ([Fe(bpm)3]2+) and high-spin iron(III) ([Fe(ox)3]3-) entities act as bidentate ligands (through two bpm-nitrogen and two oxalato-oxygen atoms, respectively) toward the univalent sodium cation, yielding the trinuclear (bpm)2Fe(II)-bpm-Na(I)-ox-Fe(III)(ox)2 complex. Two cis-coordinated water molecules complete the distorted octahedral surrounding of the sodium atom. The ranges of the Fe(II)-N(bpm) and Fe(III)-O(ox) bond distances [1.968(6)-1.993(5) and 1.992(6)-2.024(6) A, respectively] compare well with those observed in 1. The Na-N(bpm) bond lengths (2.548(7) and 2.677(7) A) are longer than those of Na-O(ox) (2.514(7) and 2.380(7) A) and Na-O(water) (2.334(15) and 2.356(12) A). The intramolecular Fe(II)...Fe(III) separation is 6.763(2) A, whereas the shortest intermolecular Fe(II)...Fe(II) and Fe(III)...Fe(III) distances are 8.152(2) and 8.992(2) A, respectively. Magnetic susceptibility measurements in the temperature range 2.0-290 K for 1 reveal that the high-spin iron(III) ions are antiferromagnetically coupled (J = -6.6 cm-1, the Hamiltonian being defined as H = -JS1.S2). The magnitude of the antiferromagnetic coupling through the bridging oxalato in the magneto-structurally characterized family of formula [M2(ox)5](2m-10)+ (M = Fe(III) (1), Cr(III), and Ni(II)) is analyzed and discussed by means of a simple orbital model.

Magnetic coupling through the carbon skeleton of malonate in two polymorphs of ([Cu(bpy)(H2O)][Cu(bpy)(mal)(H2O)])(ClO4)2 (H2mal = malonic acid; bpy = 2,2'-bipyridine).

Two polymorphic malonato-bridged copper(II) complexes of formula ([Cu(bpy)(H2O)][Cu(bpy)(mal)(H2O)])-(ClO4)2 (1 and 2) (bpy = 2,2'-bipyridine and mal = malonate dianion) have been prepared and their structures solved by X-ray diffraction methods. Compound 1 crystallizes in the monoclinic space group P2(1)/a, with a = 23.743(3) A, b = 9.7522(5) A, c = 27.731(2) A, beta = 114.580(10) degrees, and Z = 4. Compound 2 crystallizes in the orthorhombic space group Pbcn, with a = 23.700(5) A, b = 25.162(5) A, c = 9.693(5) A, and Z = 4. The structures of 1 and 2 are made up of uncoordinated perchlorate anions and malonate-bridged zigzag copper(II) chains grouped in an isosceles triangle running parallel to the b (1) and c (2) axes. These chains are built by a [Cu(bpy)(mal)(H2O)] unit acting as bis-monodentate ligand toward two [Cu(bpy)(H2O)] adjacent units through its OCCCO skeleton in an anti-anti conformation, whereas the OCO carboxylate bridges exhibit the anti-syn conformation. Compounds 1 and 2 contain four crystallographically independent copper(II) atoms, but the environment of all of them is distorted square pyramidal: the axial position is occupied by a water molecule, whereas the equatorial plane is formed by a chelating bpy and either a bidentate malonate or two carboxylate oxygens from two malonate groups. The equatorial Cu-O(mal) (1.911(4)-1.978(4) (1) and 1.897(5)-1.991(4) A (2)) and Cu-N(bpy) (1.983(4)-2.008(5) (1) and 1.971(6)-2.007(6) A (2)) bonds are somewhat shorter than the axial Cu-O(w) one (2.257(5)-2.524(5) (1) and 2.236(5)-2.505(6) A (2)). The angles subtended at the copper atom by the chelating bpy vary in the ranges 80.9(2)-81.8(2) degrees (1) and 80.4(2)-82.1(2) degrees (2), values which are somewhat smaller than those of the chelating malonate (80.4(2)-82.1(2) degrees (1) and 93.0(2)-93.6(2) degrees (2)). The intrachain copper-copper separations through the OCCCO fragment are 8.227(1) (1) and 8.206(2) A (2), whereas those through the OCO bridging unit are 4.579(1)-5.043(1) (1) and 4.572(2)-5.040(2) A (2). The magnetic behavior of 1 and 2 in the temperature range 2.0-290 K is very close, and it corresponds to an overall ferromagnetic coupling, the chi MT versus T curve exhibiting a maximum at 18 K. The analysis of the magnetic data through a numerical expression derived for the real topology of 1 and 2, that is, chains of isosceles triangles with two intrachain exchange pathways J1 (exchange coupling through the OCO carboxylate) and J2 (exchange coupling through the OCCCO malonate), indicates the occurrence of ferro- (J1 = +4.6 cm-1) and antiferromagnetic couplings (J2 = -4.2 cm-1). The magnetic coupling through these exchange pathways is further analyzed and substantiated by density functional theory calculations on a malonate-bridged trinuclear copper(II) model system.

Heterobimetallic oxalato-bridged Cu(II)Re(IV) complexes. Synthesis, crystal structure and magnetic properties.

Three copper(II)-rhenium(IV) bimetallic complexes of formula [ReCl(4)(mu-ox)Cu(phen)(2)] (1), [ReCl(4)(mu-ox)Cu(phen)(2)].CH(3)CN (2), and [ReCl(4)(mu-ox)Cu(terpy) (H(2)O)][ReCl(4)(mu-ox)Cu(terpy)(CH(3)CN)] (3) (ox = oxalate anion, phen = 1,10-phenanthroline, and terpy = 2,2':6,2"- terpyridine) have been synthesized and their crystal structures determined by single-crystal X-ray diffraction. Complex 1 crystallizes in the triclinic system, space group P(-1), with a = 9.776(2), b = 11.744(3), c = 14.183(3) A, alpha =102.09(2) degrees, beta = 109.42(2) degrees, gamma = 107.11(2) degrees, and Z = 2, whereas 2 and 3 crystallize in the monoclinic system, space groups P2(1)/n and P2(1)/c, respectively, with a = 12.837(3), b = 17.761(4), c = 12.914(3) A, beta = 91.32(2) degrees, and Z = 4 for 2, and a = 8.930(2), b = 18.543(4), c = 27.503(6) A, beta = 94.67(2) degrees, and Z = 4 for 3. The structures of 1 and 2 are made up of neutral [ReCl(4)(mu-ox)Cu(phen)(2)] bimetallic units. Re(IV) and Cu(II) metal ions exhibit distorted octahedral coordination geometries, being bridged by a bis(bidentate) oxalato ligand. The presence of acetonitrile molecules of crystallization in 2 causes a somewhat greater separation between the bimetallic complexes and a different packing of these units in the crystal structure with respect to 1. The copper-rhenium separation across oxalato is 5.628(2) in 1 and 5.649(3) A in 2. The structure of 3 is made up of two different and neutral bimetallic units, [ReCl(4)(mu-ox)Cu(terpy)(H(2)O)] and [ReCl(4)(mu-ox)Cu(terpy)(CH(3)CN)]. In the first one, the oxalate group behaves as a bis(bidentate) ligand occupying one equatorial and one axial position in the elongated octahedral environment of Cu(II). The water molecule is axially coordinated. In the second one, the oxalate group behaves as a bidentate/monodentate ligand occupying the axial position in the square pyramidal environment of Cu(II). The acetonitrile molecule occupies a basal coordination position around the copper atom. These units are arranged in such a way that a chlorine atom of the first unit (Cl(1)) points toward the copper atom (Cu(2))of the second one (3.077(2) A for Cl(1)(.)Cu(2)), forming a tetranuclear species. The copper-rhenium separation across bis(didentate) oxalato is 5.504(3) A, whereas that through bidentate/monodentate oxalato is 5.436(2) A. The magnetic behavior of 2 and 3 has been investigated over the temperature range 1.8-300 K. A very weak and nearly identical antiferromagnetic coupling between Re(IV) and Cu(II) through bis(bidentate) oxalato occurs in 2 (J = -0.90 cm(-1)) and 3 (J = -0.83 cm(-1)); it is ferromagnetic in 3 through both the bidentate-monodentate oxalato (J = +5.60 cm(-1)) and the chloro (J = +0.70 cm(-1)) bridges.

Exchange coupling in cyano-bridged homodinuclear Cu(II) and Ni(II) complexes: synthesis, structure, magnetism, and density functional theoretical study.

The synthesis and structural characterization of several new cyano-bridged copper(II) and nickel(II) homodinuclear complexes is presented. The measure of magnetic properties for these complexes is complemented with a computational study of the exchange coupling for several model structures representing this family of compounds. The influence of several factors on the coupling constant has been examined, coordination position occupied by the bridging ligand, distortions of the coordination environment, and relative disposition of the cyanide ion with respect to the M-M vector. Comparison of experimental and calculated coupling constants allows for the rationalization of the most relevant features of the exchange interaction between two identical metal ions through a cyano bridge.