Complications of the Superior Eyelid Endoscopic Transorbital Approach to the Skull Base: Preliminary Experience With Specific Focus on Orbital Outcome.

BACKGROUND: The endoscopic superior eyelid approach is a relatively novel mini-invasive technique that is currently investigating for skull base cancers. However, questions remain regarding specific approach-related complications when treating different skull base tumors. This study aims to analyze any surgical complications that occurred in our preliminary consecutive experience, with specific focus on orbital outcome. METHODS: A retrospective and consecutive cohort of patients treated via a superior eyelid endoscopic transorbital approach at the Division of Neurosurgery of the Hospital Clinic in Barcelona was analyzed. Patients features were described in detail. Complications were divided into 2 groups to analyze separately the approach-related complications, and those resulting from tumor removal. The ocular complications were subdivided into early ocular status (<3 weeks), late ocular status (3-8 weeks), and persistent ocular complications. The "Park questionnaire" was used to determine patient's satisfaction related to the transorbital approach. RESULTS: A total of 20 patients (5 spheno-orbital meningiomas, 1 intradiploic Meningioma, 2 intraconal lesions, 1 temporal pole lesion, 2 trigeminal schwannoma, 3 cavernous sinus lesions, and 6 petroclival lesions) were included in the period 2017-2022. Regarding early ocular status, upper eyelid edema was detected in all cases (100%) associated with diplopia in the lateral gaze in 30% of cases, and periorbital edema in 15% of cases. These aspects tend to resolve at late ocular follow-up (3-8 weeks) in most cases. Regarding persistent ocular complications, in one case of intraconal lesion, a limitation of eye abduction was detected (5%). In another patient with intraconal lesion, an ocular neuropathic pain was reported (5%). In 2 cases of petroclival menigioma, who were also treated with a ventriculo-peritoneal shunt, slight enophthalmus was observed as a persistent complication (10%). According to the Park questionnaire, no cosmetic complaints, no head pain, no palpable cranial irregularities, and no limited mouth opening were reported, and an average of 89% of general satisfaction was encountered. CONCLUSIONS: The superior eyelid endoscopic transorbital approach is a safe and satisfactory technique for a diversity of skull base tumors. At late follow-up, upper eyelid edema, diplopia, and periorbital edema tend to resolve. Persistent ocular complications are more frequent after treating intraconal lesions. Enophthalmus may occur in patients with associated ventriculo-peritoneal shunt. According to patient's satisfaction, fairly acceptable results are attained.

Effects on cerebral blood flow of position changes, hyperoxia, CO2 partial pressure variations and the Valsalva manoeuvre: A study in healthy volunteers.

BACKGROUND: Maintaining adequate blood pressure to ensure proper cerebral blood flow (CBF) during surgery is challenging. Induced mild hypotension, sitting position or unavoidable intra-operative circumstances such as haemorrhage, added to variations in carbon dioxide and oxygen tensions, may influence perfusion. Several of these circumstances may coincide and it is unclear how these may affect CBF. OBJECTIVE: To describe the variation in transcranial Doppler and regional cerebral oxygen saturation (rSO2), as a surrogate of CBF, after cardiac preload and gravitational positional changes. DESIGN: Observational study. SETTING: Operating room at Hospital Clínic de Barcelona. VOLUNTEERS: Ten healthy volunteers, white, both sexes. INTERVENTIONS: Measurements were performed in the supine, sitting and standing positions during hyperoxia, hypocapnia and hypercapnia protocols and after a Valsalva manoeuvre. MAIN OUTCOME MEASURES: Cardiac index (CI), haemodynamic and respiratory variables, maximal and mean velocities (Vmax, Vmean) (transcranial Doppler) and rSO2 were acquired. Results were analysed using a generalised estimating equation technique. RESULTS: CI increases more than 16% after a preload challenge were not accompanied by differences in rSO2 or Vmax - Vmean. With positional changes, Vmean decreased more than 7% (P = 0.042) from the supine to the seated position. Hyperoxia induced a cerebral rSO2 increase more than 6% (P = 0.0001) with decreases in Vmax, Vmean and CI values more than 3% (P = 0.001, 0.022 and 0.001) in the supine and standing position. During hypocapnia, CI rose more than 20% from supine to seated and standing (P = 0.0001) with a 4.5% decrease in cerebral rSO2 (P = 0.001) and a decrease of Vmax - Vmean more than 24% in all positions (P = 0.001). Hypercapnia increased cerebral rSO2 more than 17% (P = 0.001), Vmax - Vmean more than 30% (P = 0.001) with no changes in CI. After a Valsalva manoeuvre, rSO2 decreased more than 3% in the right hemisphere in the upright position (P = 0.001). Vmax - Vmean decreased more than 10% (P = 0.001) with no changes in CI. CONCLUSION: CBF changes in response to cerebral vasoconstriction and vasodilatation were detected with rSO2 and transcranial Doppler in healthy volunteers during cardiac preload and in different body positions. Acute hypercapnia had a greater effect on recorded brain parameters than hypocapnia.

Neurophysiologic Monitoring of Oculomotor Nerves During Transorbital Surgery: Proof of Concept and Anatomic Demonstration.

BACKGROUND AND OBJECTIVES: Transorbital neuroendoscopic surgery (TONES) is continuously evolving and gaining terrain in approaching different skull base pathologies. The objective of this study was to present our methodology for introducing recording electrodes, which includes a new transconjunctival pathway, to monitor the extraocular muscle function during TONES. METHODS: A translational observational study was performed from an anatomic demonstration focused on the transconjunctival electrode placement technique to a descriptive analysis in our series of 6 patients operated using TONES in association with intraoperative neurophysiologic monitoring of the oculomotor nerves from 2017 to 2023. The stepwise anatomic demonstration for the electrode placement and correct positioning in the target muscle was realized through cadaveric dissection. The descriptive analysis evaluated viability (obtention of the electromyography in each cranial nerve [CN] monitored), security (complications), and compatibility (interference with TONES). RESULTS: In our series of 6 patients, 16 CNs were correctly monitored: 6 (100%) CNs III, 5 (83.3%) CNs VI, and 5 (83.3%) CNs IV. Spontaneous electromyography was registered correctly, and compound muscle action potential using triggered electromyography was obtained for anatomic confirmation of structures (1 CN III and VI). No complications nor interference with the surgical procedure were detected. CONCLUSION: The methodology for introducing the recording electrodes was viable, secure, and compatible with TONES.

Deep brain stimulation and digital monitoring for patients with treatment-resistant schizophrenia and bipolar disorder: A case series.

AIM: The use of deep brain stimulation (DBS) has been recently extended for treating resistant psychiatric disorders, but the experience in patients with schizophrenia-related disorders and bipolar disorder (BD) is scarce. METHOD: We conducted an observational, one-year longitudinal study to evaluate the effects of DBS in four treatment-resistant patients with schizophrenia, schizoaffective, and BD, included in a pilot, last-resource protocol. Patients were digitally monitored for objective assessment of behavioral changes. RESULTS: After one year of its initiation, DBS of the nucleus accumbens (in subjects N2, N3, and N4) and subgenual anterior cingulate cortex (in N1) produced a significant clinical improvement, associated with decreases in the Clinical Global Impression (from 5.25±0.5 to 3.5±1, p=0.035) and in the Hamilton Depression Rating Scale (HADRS scores, from 14.5±6.56 to 1.5±1.29, p=0.020). We observed a notable, durable therapeutic response in two patients from this cohort (N1 and N3), a clinically relevant relief in a third (N2), and a lack of a significant response in the last one (N4). Maintenance electroconvulsive therapy sessions could be discontinued in the three patients that responded to DBS (N1-3). There were no side effects or relevant changes in cognitive functioning. There were relevant differences between physical activity and sleep time among the four participants. CONCLUSIONS: These results suggest initial evidence that DBS may be an effective and safe alternative for treating complex and resistant forms of schizophrenia-related disorders and BD. Digital monitoring may help to capture objective measures of behavioral changes after the intervention.

Association between preoperative serum lactate concentrate with tumor cell proliferative index in primary brain tumor.

BACKGROUND: Elevated preoperative lactate levels have been reported in patients admitted for resection of brain tumors. As histologic type and tumor grade have also been linked to lactate concentration, we hypothesized that preoperative lactate concentration in patients with brain tumors may be associated with tumor proliferation. We describe the relationship between preoperative plasma lactate levels, and the cell proliferation marker Ki-67 in brain tumor surgery. METHODS: In this cross-sectional study, records of patients who underwent craniotomy between June 2017 and February 2018 at our Hospital were reviewed to select glioma and meningioma cases in which lactate concentrations in plasma and degree of cell proliferation were registered. Bivariable and linear regression analyses were used to assess the association between lactate concentrations and the Ki-67 Index. RESULTS: Lactate concentrations in plasma and Ki-67 Index were available in 55 patients. Meningioma cases had a mean concentration of 1.2 (0.1) mmol/L compared to diffuse astrocytic and oligodendroglial tumors cases with 1.7 (0.1) mmol/L (P<0.01). Both variables had a low positive correlation in meningiomas (Spearman's r, 0.29; 95% CI, -0.10-0.61; P=0.13) and a high correlation in gliomas (Spearman's r, 0.64; 95% CI, 0.33-0.82; P<0.01). The pooled analysis showed a high correlation index (Spearman's r, 0.61; 95% CI, 0.40-0.76; P<0.01). A linear regression model showed that the Ki-67 Index explained 43% of the variation in lactate (P<0.01). CONCLUSIONS: Brain tumors with higher rates of cell proliferation have higher plasma lactate levels. In this scenario, lactate concentrations may not only reflect systemic perfusion.

Hemodynamic Response, Coughing and Incidence of Cerebrospinal Fluid Leakage on Awakening with an Endotracheal Tube or Laryngeal Mask Airway in Place after Transsphenoidal Pituitary Surgery: A Randomized Clinical Trial.

We aimed to compare systemic and cerebral hemodynamics and coughing during emergence after pituitary surgery after endotracheal tube (ETT) extubation or after replacing ETT with a laryngeal mask airway (LMA). Patients were randomized to awaken with an ETT in place or after replacing it with an LMA. We recorded mean arterial pressure (MAP), heart rate, middle cerebral artery (MCA) flow velocity, regional cerebral oxygen saturation (SrO2), cardiac index, plasma norepinephrine, need for vasoactive drugs, coughing during emergence, and postoperative cerebrospinal fluid (CSF) leakage. The primary endpoint was postoperative MAP; secondary endpoints were SrO2 and coughing incidence. Forty-five patients were included. MAP was lower during emergence than at baseline in both groups. There were no significant between-group differences in blood pressure, nor in the number of patients that required antihypertensive drugs during emergence (ETT: 8 patients (34.8%) vs. LMA: 3 patients (14.3%); p = 0.116). MCA flow velocity was higher in the ETT group (e.g., mean (95% CI) at 15 min, 103.2 (96.3-110.1) vs. 89.6 (82.6-96.5) cm·s-1; p = 0.003). SrO2, cardiac index, and norepinephrine levels were similar. Coughing was more frequent in the ETT group (81% vs. 15%; p < 0.001). CSF leakage occurred in three patients (13%) in the ETT group. Placing an LMA before removing an ETT during emergence after pituitary surgery favors a safer cerebral hemodynamic profile and reduces coughing. This strategy may lower the risk for CSF leakage.

Discovering the complex chemistry of a simple Ni(II)/H(3)L system: magnetostructural characterization and DFT calculations of Di- and polynuclear nickel(II) compounds.

The simple nickel(II) acetate/H(3)L system (H(3)L = 2-(2-hydroxyphenyl)-1,3-bis[4-(2-hydroxyphenyl)-3-azabut-3-enyl]-1,3-imidazolidine) presents an unusually complicated reactivity scheme, which strongly depends on the Ni(OAc)(2)/H(3)L molar ratio and on the pH of the medium. Thus, in addition to the formerly reported compounds [Ni(2)L(OAc)(H(2)O)(2)][Ni(2)L(OAc)(H(2)O)(HOAc)].3.25H(2)O, 1.3.25H(2)O; [{Ni(3)L(OAc)(OH)(H(2)O)(MeOH)(2)}(CO(3)){Ni(2)L(OAc)(MeOH)(2)}].2.7H(2)O.1.5MeOH, 2.2.7H(2)O.1.5MeOH; and [Ni(3)L(OAc)(2)(OH)(H(2)O)(MeOH)(2)].3H(2)O.0.5MeOH, 3.3H(2)O.0.5MeOH, this system can also yield some other complexes as [Ni(2)L(o-O-C(6)H(4)-CHO)(H(2)O)].1.75H(2)O, 4.1.75H(2)O; [Ni(2)L(OH)(H(2)O)(MeOH)].3H(2)O.1.5MeOH, 5.3H(2)O.1.5MeOH; [Ni(2)L(OAc)(MeOH)(2)].H(2)O.3MeOH, 6.H(2)O.3MeOH; and [{Ni(2)L(MeOH)}(CO(3)){Ni(2)L(MeOH)(2)}].4.75H(2)O.2MeOH, 7.4.75H(2)O.2MeOH. A detailed study of the reaction scheme that allows obtaining all of these complexes is presented herein, as well as the structural characterization of the novel compounds 4.1.75H(2)O to 7.4.75H(2)O.2MeOH. X-ray analyses show that all of them present stereoisomery in the solid state. In this way, 6.H(2)O.3MeOH appears particularly interesting, as its molecular and supramolecular chirality is only controlled by hydrogen bonds. Magnetic studies of 5.3H(2)O to 7.4.75H(2)O.2MeOH are also discussed, and the complicated magnetic superexchange pathway shown by 7.4.75H(2)O.2MeOH is analyzed in light of DFT calculations.

Safety and Feasibility Assessment of the O-Arm as an Intraoperative Angiography Device in Aneurysm Surgery.

OBJECTIVE: To describe the technique and initial experience of using a rotational 3-dimensional (3D) fluoroscopy system (O-arm; Medtronic) as intraoperative angiography (IA) in the surgery of cerebral aneurysms. METHODS: The 3D IA with O-arm (IAWOA) was performed in a consecutive cohort of patients with unruptured intracranial aneurysms. Conventional microsurgical clipping was performed with the assistance of indocyanine green videoangiography. Then the O-arm chassis was brought in, the ipsilateral internal carotid artery was catheterized, and contrasted images were acquired. Resulting datasets were exported in Digital Imaging and Communications in Medicine and processed using the Osirix software in an accessory computer. The 3D image reconstruction was evaluated intraoperatively to confirm aneurysm occlusion and parent vessel patency. Afterward, agreement among IAWOA, indocyanine green videoangiography, and standard postoperative angiography was analyzed. RESULTS: The initial pilot study was performed in 6 patients with 7 unruptured aneurysms. The aneurysm occlusion rate was 100%. The concordance of the IAWOA and the standard postoperative angiography was complete, both in terms of occlusion and parent vessel patency. No complications derived from the IAWOA were observed except in 1 patient, who presented a retroperitoneal hematoma without clinical consequences. CONCLUSIONS: The 3D rotational fluoroscopy (O-arm) device could be safely and effectively used as an IA system in selected patients. To the best of our knowledge, this is the first study reporting its use as an IA device. This technique seems to offer excellent image quality that could be compared with that of the gold standard 3D digital subtraction angiography but with a lower cost and versatility of use for other subspecialties.

Magnetic structure of the large-spin Mn10 and Mn19 complexes: a theoretical complement to an experimental milestone.

High-spin molecules have been proposed as candidates for the storage of information at the molecular level. The electronic structure of two complex magnetic molecular systems, Mn 10 and Mn 19, is characterized by means of a computational study based on density functional theory. All the exchange interactions in the recently reported Mn 19 complex with the highest known spin value of 83/2, and in its highly symmetric Mn 10 parent compound, are ferromagnetic. In these complexes, there are two kinds of ferromagnetic coupling: the first one corresponds to Mn (II)-Mn (III) interactions through a double mu 2-alkoxo-mu 4-oxo bridge where the high coordination number of the Mn (II) cations results in long Mn (II)-O bond distances, while the second one involves Mn (III)-Mn (III) interactions through mu 2-alkoxo-mu 3-eta (1):eta (1):eta (1) azido bridging ligands with long Mn (III)-N distances due to a Jahn-Teller effect.

2D copper(II) complex built from N-methyl-1,3-diamino-2-propanolate and azide ligands: structure, magnetic, and DFT studies.

The synthesis, structural characterization, and magnetic behavior of a new 2D copper(II) compound with formula {[Cu2(mu-O2CMe)(mu-MedapO)(mu1,1-N3)2]n (CH3OH)n} 1, in which MedapOH is N-methyl-1,3-diamino-2-propanol is reported herein. 1 crystallizes in the triclinic system, space group P1, with unit cell parameters a = 6.688(5) A, b = 10.591(6) A, c = 12.100(7) A, alpha = 113.01(3) degrees, beta = 105.08(4) degrees, gamma = 93.93(3) degrees, Z = 2. The structure of 1 consists of neutral alternate 1D chains formed by the sequence of [Cu(1)-(mu1,1-N3)2-Cu(1)-(MedapO/acetate)-Cu(2)-(mu1,1-N3)2-Cu2)]. Each dinuclear [Cu(1)-Cu(2)] unit interacts with similar dinuclear units of neighbor chains in basis to large Cu-N(azido) distances to give a 2D arrangement. The magnetic behavior of 1 has been checked giving a net ferromagnetic coupling. The fit of the chiM versus T data as dinuclear compound affords a J value of 53.0 cm(-1) as a consequence of the orbital countercomplementarity phenomenon. The exchange pathways have been justified by density functional calculations.

Synthesis of two new linear trinuclear Cu(II) complexes: mechanism of magnetic coupling through hybrid B3LYP functional and CShM studies.

Two new Cu(II) linear trinuclear Schiff base complexes, [Cu3(L)2(CH3COO)2] (1) and [Cu3(L)2(CF3COO)2] (2), have been prepared using a symmetrical Schiff base ligand H2L [where H2L = N,N'-bis(2-hydroxyacetophenone)propylenediimine]. Both of the complexes have been characterized by elemental analyses, Fourier transform IR, UV/vis, and electron paramagnetic resonance spectroscopy. Single-crystal X-ray structures show that the adjacent Cu(II) ions are linked by double phenoxo bridges and a mu(2)-eta(1):eta(1) carboxylato bridge. In each complex, the central copper atom is located in an inversion center with distorted octahedral coordination geometry, while the terminal copper atoms have square-pyramidal geometry. Cryomagnetic susceptibility measurements over a wide range of temperature exhibit a distinct antiferromagnetic interaction of J = -36.5 and -72.3 cm(-1) for 1 and 2, respectively. Density functional theory calculations (B3LYP functional) and continuous-shape measurement (CShM) studies have been performed on the trinuclear unit to provide a qualitative theoretical interpretation of the antiferromagnetic behavior shown by the complexes.

Laryngeal Mask Ventilation During Lumbar Spine Neurosurgery in Knee-Chest Position is Feasible.

BACKGROUND: This study describes our experience with laryngeal mask (LM) inserted after anesthetic induction in patients already in knee-chest position for lumbar neurosurgery. METHODS: Airway management (need for LM repositioning, orotracheal intubation because of failed LM insertion), anticipated difficult airway, and airway complications were registered. Statistics were compared between groups with the t test or the χ test, as appropriate. RESULTS: A total of 358 cases were reviewed from 2008 to 2013. Tracheal intubation was performed in 108 patients and LM was chosen for 250 patients (69.8%). Intubated patients had a higher mean age and rate of anticipated difficult airway; duration of surgery was longer (P<0.001, all comparisons). LM insertion and anesthetic induction proved effective in 97.2% of the LM-ventilated patients; 7 patients (2.8%) were intubated because of persistent leakage. Incidences with airway management were resolved without compromising patient safety. CONCLUSION: LM airway management during lumbar neurosurgery in knee-chest position is feasible for selected patients when the anesthetist is experienced.

ProSeal Laryngeal Mask Airway Attenuates Systemic and Cerebral Hemodynamic Response During Awakening of Neurosurgical Patients: A Randomized Clinical Trial.

BACKGROUND: Extubation and emergence from anesthesia may lead to systemic and cerebral hemodynamic changes that endanger neurosurgical patients. We aimed to compare systemic and cerebral hemodynamic variables and cough incidence in neurosurgery patients emerging from general anesthesia with the standard procedure (endotracheal tube [ETT] extubation) or after replacement of the ETT with a laryngeal mask airway (LMA). MATERIALS AND METHODS: Forty-two patients undergoing supratentorial craniotomy under general anesthesia were included in a randomized open-label parallel trial. Patients were randomized (sealed envelopes labeled with software-generated randomized numbers) to awaken with the ETT in place or after its replacement with a ProSeal LMA. We recorded mean arterial pressure as the primary endpoint and heart rate, middle cerebral artery flow velocity, regional cerebral oxygen saturation, norepinephrine plasma concentrations, and coughing. RESULTS: No differences were found between groups at baseline. All hemodynamic variables increased significantly from baseline in both groups during emergence. The ETT group had significantly higher mean arterial pressure (11.9 mm Hg; 95% confidence interval [CI], 2.1-21.8 mm Hg) (P=0.017), heart rate (7.2 beats/min; 95% CI, 0.7-13.7 beats/min) (P=0.03), and rate-pressure product (1045.4; 95% CI, 440.8-1650) (P=0.001). Antihypertensive medication was administered to more ETT-group patients than LMA-group patients (9 [42.9%] vs. 3 [14.3%] patients, respectively; P=0.04). The percent increase in regional cerebral oxygen saturation was greater in the ETT group by 26.1% (95% CI, 9.1%-43.2%) (P=0.002), but no between-group differences were found in MCA flow velocity. Norepinephrine plasma concentrations rose in both groups between baseline and the end of emergence: LMA: from 87.5±7.1 to 125.6±17.3 pg/mL; and ETT: from 118.1±14.1 to 158.1±24.7 pg/mL (P=0.007). The differences between groups were not significant. The incidence of cough was higher in the ETT group (87.5%) than in the LMA group (9.5%) (P<0.001). CONCLUSIONS: Replacing the ETT with the LMA before neurosurgical patients emerge from anesthesia results in a more favorable hemodynamic profile, less cerebral hyperemia, and a lower incidence of cough.

Synthesis and characterization of [Cu(Me2oxpn)Ni(NO2)(tmen)](ClO4): a single ferrimagnetic dinuclear CuII-NiII complex acting as weak molecule-based magnet.

The new heterodinuclear complex [Cu(Me2oxpn)Ni(NO2)(tmen)](ClO4), that exhibits strong antiferromagnetic intramolecular coupling between CuII and NiII ions (ferrimagnetic behavior), shows ferromagnetic ordering at low temperature, due likely to a small canting phenomenon; it is one of the very few compounds made from isolated molecules that lead to cooperative magnetic behavior.

Pressure inside the neuroendoscope: correlation with epidural intracranial pressure during neuroendoscopic procedures.

BACKGROUND: During neuroendoscopic procedures, pressure inside the neuroendoscope (PIN) monitored through the irrigation channel correlates with the occurrence of postoperative complications. Our aim was to analyze the reliability of PIN measurement as a surrogate for intracranial pressure (ICP) by comparing PIN with simultaneously epidural ICP measurement as the standard. METHODS: Seventeen consecutive patients undergoing neuroendoscopy were studied prospectively. Type and length of procedure and PIN and epidural ICP values during neuroendoscopy were recorded. Lin's concordance coefficient and Bland-Altman analysis of agreement were used to assess correspondence between the 2 systems. RESULTS: A consistent relation between PIN and epidural ICP waveforms was observed during neuroendoscopic navigation. A strong Pearson correlation between PIN and epidural ICP data were found in 15 patients. Epidural ICP values were systematically higher than PIN values in 15 patients. Lin concordance coefficients showed moderate global agreement between the 2 methods, at 0.58 (95% confidence interval, 0.577-0.592). In 6 cases (35.2%) concordance was good according to this analysis, in 7 cases (41.2%) agreement was moderate/fair, and in 4 cases (23.5%) agreement was poor. The Bland-Altman analysis of patient data showed good agreement between the PIN and epidural ICP measurements for most patients, although discrepancies were greater at higher ICP values for 11 patients. Bland-Altman analysis of the complete dataset, after the normalization of individual's measurements, showed good overall agreement. CONCLUSIONS: PIN measurement seems useful for evaluating ICP changes related to neuroendoscopic procedures and seems to be more consistent than epidural ICP at high pressures.

Ferro- and anti-ferromagnetically coupled tetracopper(II) 2 x 2 homoleptic rectangular grids supported by both mu-O and mu-(N-N) bridges derived from a new pyrazole based polydentate Schiff base ligand-magneto-structural correlations and DFT calculation.

The pyrazole derived Schiff base polytopic ligand 5-methyl-N'-[1-(pyridin-2-yl)ethylidene]-1H-pyrazole-3-carbohydrazide (PzCAP), prepared by the reaction between 5-methylpyrazole-3-carbohydrazide and 2-acetyl pyridine, has two potentially bridging functional groups [mu-O and mu-(N-N)] and consequently can exhibit different coordination conformations. Two tetranuclear homoleptic copper(II) 2 x 2 rectangular grid-complexes [Cu(4)(PzCAP)(4)(NO(3))(2)] (NO(3))(2).8H(2)O (1) and [Cu(4)(PzCAP)(4)(ClO(4))(2)] (ClO(4))(2) (2) were formed by a strict self-assembly process employing metal and ligand under 1:1 mol proportion. Each pair of the ligand molecules in the two complexes are arranged in roughly parallel fashion but under different conformations. The ligand PzCAP contains terminal pyridine and pyrazole residues bound to a central flexible diazine subunit (N-N). The rectangular Cu(II) 2 x 2 grid complexes having [Cu(4)(mu-N-N)(2)(mu-O)(2)] core involve a mixture of two diazine (Cu-N-N-Cu approximately 160 degrees ) and two alkoxo (Cu-O-Cu approximately 138 degrees ) bridges along the length and breadth respectively. In the [Cu(4)(mu-N-N)(2)(mu-O)(2)] core in , out of the four Cu(II) centers, all are hexa-coordinated but there are two penta-coordinated and two hexa-coordinated Cu(II) centers in the same core of . Each complex having the central [Cu(4)(mu-N-N)(2)(mu-O)(2)] core, exhibits quite different magnetic interactions among the metal centers. The paramagnetic Cu(II) centers bridged through the diazine fragment are involved in anti-ferromagnetic interaction while a dominant ferromagnetic interaction prevails between the alkoxo-bridged Cu(II) centers. The [Cu(4)(mu-N-N)(2)(mu-O)(2)] cluster in shows both ferromagnetic and anti-ferromagnetic interaction (J(1) = -0.80 cm(-1) and J(2) = +3.49 cm(-1)), a very unusual characteristic in this system while the same cluster in exhibits dominant anti-ferromagnetic coupling (J(1) = -89.1 cm(-1) and J(2) = +5.5 cm(-1)) through the trans Cu-(N-N)-Cu bridging arrangement, typical for systems of this sort. Both the complexes and have been characterized structurally, magnetically and spectroscopically. The exchange pathways parameters (J(1) and J(2)) have also been evaluated from density functional theoretical calculations to corroborate the bridging signatures with experimental findings.

Structure, magnetic properties, polarized neutron diffraction, and theoretical study of a copper(II) cubane.

The paper reports the synthesis, X-ray and neutron diffraction crystal structures, magnetic properties, high field-high frequency EPR (HF-EPR), spin density and theoretical description of the tetranuclear CuII complex [Cu4L4] with cubane-like structure (LH2=1,1,1-trifluoro-7-hydroxy-4-methyl-5-aza-hept-3-en-2-one). The simulation of the magnetic behavior gives a predominant ferromagnetic interaction J1 (+30.5 cm(-1)) and a weak antiferromagnetic interaction J2 (-5.5 cm(-1)), which correspond to short and long Cu-Cu distances, respectively, as evidence from the crystal structure [see formulate in text]. It is in agreement with DFT calculations and with the saturation magnetization value of an S=2 ground spin state. HF-EPR measurements at low temperatures (5 to 30 K) provide evidence for a negative axial zero-field splitting parameter D (-0.25+/-0.01 cm(-1)) plus a small rhombic term E (0.025+/-0.001 cm(-1), E/D = 0.1). The experimental spin distribution from polarized neutron diffraction is mainly located in the basal plane of the CuII ion with a distortion of yz-type for one CuII ion. Delocalization on the ligand (L) is observed but to a smaller extent than expected from DFT calculations.

An orthogonal ferromagnetically coupled tetracopper(II) 2 x 2 homoleptic grid supported by micro-O4 bridges and its DFT study.

A pyrazole based ditopic ligand (PzOAP), prepared by the reaction between 5-methylpyrazole-3-carbohydrazide and methyl ester of imino picolinic acid, reacts with Cu(NO3)2.6H2O to form a self-assembled, ferromagnetically coupled, alkoxide bridged tetranuclear homoleptic Cu(II) square grid-complex [Cu4(PzOAP)4(NO3)2] (NO3)2.4H2O (1) with a central Cu4[micro-O4] core, involving four ligand molecules. In the Cu4[micro-O4] core, out of four copper centers, two copper centers are penta-coordinated and the remaining two are hexa-coordinated. In each case of hexa-coordination, the sixth position is occupied by the nitrate ion. The complex 1 has been characterized structurally and magnetically. Although Cu-O-Cu bridge angles are too large (138-141 degrees) and Cu-Cu distances are short (4.043-4.131 A), suitable for propagation of expected antiferromagnetic exchange interactions within the grid, yet intramolecular ferromagnetic exchange (J = 5.38 cm(-1)) is present with S = 4/2 magnetic ground state. This ferromagnetic interaction is quite obvious from the bridging connections (d(x2-y2)) lying almost orthogonally between the metal centers. The exchange pathways parameters have been evaluated from density functional calculations.

Exchange coupling in transition-metal complexes via density-functional theory: comparison and reliability of different basis set approaches.

Theoretical methods based on density-functional theory with Gaussian, plane waves, and numerical basis sets were employed to evaluate the exchange coupling constants in transition-metal complexes. In the case of the numerical basis set, the effect of different computational parameters was tested. We analyzed whether and how the use of pseudopotentials affects the calculation of the exchange coupling constants. For the three different basis sets, a comparison of the exchange coupling constants and spin distributions shows that both the plane-wave and the numerical basis set approaches are accurate and reliable alternatives to the more established Gaussian basis functions.

Unexpected ferromagnetic interaction in a new tetranuclear copper(II) complex: synthesis, crystal structure, magnetic properties, and theoretical studies.

The new tetranuclear carbonate complex [Cu2L)2(CO3)] x 8H2O (1 x 8H2O) (H3L = (2-(2-hydroxyphenyl)-1,3-bis[4-(2-hydroxyphenyl)-3-azabut-3-enyl]-1,3-imidazolidine) has been obtained by two different synthetic routes and fully characterized. Recrystallization of 1 x 8H2O in methanol yields single crystals of {[(Cu2L)2(CO3)]}2 x 12H2O (1 x 6H2O), suitable for X-ray diffraction studies. The crystal structure of 1 x 6H2O shows two crystallographically different tetranuclear molecules in the asymmetric unit, 1a and 1b. Both molecules can be understood as self-assembled from two dinuclear [Cu2L]+ cations, joined by a mu4-eta(2):eta(1):eta(1) carbonate ligand. The copper atoms of each crystallographically different [(Cu2L)2(CO3)] molecule present miscellaneous coordination polyhedra: in both 1a and 1b, two metal centers are in square pyramidal environments, one displays a square planar chromophore and the other one has a geometry that can be considered as an intermediate between square pyramid and trigonal bipyramid. Magnetic studies reveal net intramolecular ferromagnetic coupling between the metal atoms. Density functional calculations allow the assignment of the different magnetic coupling constants and explain the unexpected ferromagnetic behavior, because of the presence of an unusual NCN bridging moiety and countercomplementarity of the phenoxo (or carbonate) and NCN bridges.