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1.
Artigo em Inglês | MEDLINE | ID: mdl-32715591

RESUMO

Thermally stable organic diradicals with a triplet ground state along with large singlet-triplet energy gap have significant potential for advanced technological applications. A series of phenylene-bridged diradicals with oxoverdazyl and nitronyl nitroxide units were synthesized via a palladium-catalyzed cross-coupling reaction of the corresponding iodoverdazyls with a nitronyl nitroxide-2-ide gold(I) complex with high yields (up to 82%). The synthesized diradicals exhibit high stability and do not decompose in an inert atmosphere up to 180 °C. The magnetic properties of prepared phenylene-coupled diradicals were investigated and magneto-structural correlations were established. For the studied diradicals, both substantial antiferromagnetic (D E ST ¼ -64 cm -1 ) and ferromagnetic (D E ST ³ 25 and 100 cm -1 ) intramolecular exchange interactions were observed. The sign of the exchange interaction is determined both by the bridging moiety ( para - or meta -phenylene) and by the type of oxoverdazyl block ( C -linked or N -linked). Upon crystallization, diradicals with the triplet ground state form unique one-dimensional exchange-coupled chains with strong intra- and weak inter-diradical ferromagnetic coupling.

2.
Dalton Trans ; 48(28): 10723-10732, 2019 Jul 16.
Artigo em Inglês | MEDLINE | ID: mdl-31246209

RESUMO

The new bis-o-iminobenzosemiquinonate nickel and cobalt complexes (imSQt-Bu)2M (M = Ni (1), Co (2)), where imSQ is a radical anion of 4,6-di-tert-butyl-N-(tert-butyl)-o-iminobenzoquinone, were synthesized and characterized in detail. The molecular structures of 1 and 2 have been established by single-crystal X-ray analysis. The metal atoms in 1 and 2 have a distorted tetrahedral environment, and the dihedral angles between the planes of two radical imSQ ligands are approximately 80° in both complexes. According to the structural and spectroscopy data along with magnetic susceptibility measurements the electronic structure of the complexes should be interpreted definitely as a high spin metal center NiII (d8, S = 1) in 1 and CoII (d7, S = 3/2) in 2 bonded with two o-iminobenzosemiquinonate radicals (Srad = 1/2). The strong antiferromagnetic metal-ligand spin interactions in both complexes lead to the observed St = 0 and St = 1/2 ground states in 1 and 2, respectively. The computational DFT UB3LYP/6-311++G(d,p) studies performed on 1 and 2 are in good agreement with experimental data. Complexes 1 and 2 have similar electrochemical properties. The electrochemical reduction of the complexes includes two quasi-reversible one-electron-transfer waves in the cathodic region corresponding to the formation of the anions [M(AP)2]2- and [(imSQ)M(AP)]1- (AP - dianion of 4,6-di-tert-butyl-N-(tert-butyl)-o-iminobenzoquinone), while in the anodic region only one quasi-reversible redox process was registered. All redox processes are shown to be ligand-based.

3.
Dalton Trans ; 48(28): 10516-10525, 2019 Jul 16.
Artigo em Inglês | MEDLINE | ID: mdl-31225849

RESUMO

A square-planar bis-o-semiquinonato nickel complex interacts with N,N'-disubstituted 1,4-diazabutadienes-1,3 forming six-coordinate compounds. The X-ray structural study indicates complex geometry to be close to the octahedral. Magnetic properties are determined by metal-ligand ferromagnetic exchange interactions which are promoted by complex geometry. In polar solvents (THF, CH2Cl2, and CHCl3) complexes are partly dissociated into corresponding diazabutadiene-nickel catecholate and free o-quinone. In the case of the most sterically hindered 1,4-bis-(2,6-di-iso-propylphenyl)-2,3-dimethyl-1,4-diazabutadiene-1,3 in n-hexane or toluene the above-mentioned reaction is accompanied by the coupling through the back-bonded methyl groups of diazabutadiene. The organic product of the coupling was eliminated from the complex, isolated and structurally characterized. Taking into account the quantitative yield the coupling reaction is the actual procedure for the synthesis of new potential nitrogen ligands.

4.
Inorg Chem ; 58(10): 6811-6820, 2019 May 20.
Artigo em Inglês | MEDLINE | ID: mdl-31067041

RESUMO

Two new isostructural microporous coordination frameworks [Mn3(Hpdc)2(pdc)2] (1) and [Mg3(Hpdc)2(pdc)2] (2) (pdc2- = pyridine-2,4-dicarboxylate) showing primitive cubic (pcu) topology have been prepared and characterized. The pore aperture of the channels is too narrow for the efficient adsorption of N2; however, both compounds demonstrate substantially higher uptake of CO2 (119.9 mL·g-1 for 1 and 102.5 mL·g-1 for 2 at 195 K, 1 bar). Despite of their structural similarities, 2 shows a typical reversible type I isotherm for adsorption/desorption of CO2, while 1 features a two-step adsorption process with a very broad hysteresis between the adsorption and desorption curves. This behavior can be explained by a combination of density functional theory calculations, sorption, and X-ray diffraction analysis and gives insights into the further development of new sorbents showing adsorption/desorption hysteresis.

5.
Dalton Trans ; 47(42): 15049-15060, 2018 Oct 30.
Artigo em Inglês | MEDLINE | ID: mdl-30303221

RESUMO

The tetracoordinated square-planar CoIII complex (imSQC(O)Ph)CoIII(APC(O)Ph) (1) bearing a radical anion and the closed-shell o-amidophenolate forms of the functionalized o-aminophenol H2LC(O)Ph were synthesized. The intermediate spin state (SCo = 1) CoIII center was found for compound 1. The cyclic voltammogram of derivative 1 contains two oxidative processes and one reductive redox process as well as an additional multi-electron wave at high negative potentials above -2 V, which can involve both the ligand and metal center. One-electron oxidation of 1 by silver triflate produces the [(imSQC(O)Ph)CoII(imQC(O)Ph)]OTf·2toluene (2) derivative with the trigonal prismatic coordination environment of the metal arising from the additional coordination of -C(O)Ph hemilabile groups. This is a first example of a trigonal prismatic coordination polyhedron in cobalt-based complexes featuring o-iminobenzoquinone ligands. The trigonal prismatic geometry achieved by the unique flexibility of the ligand allows metal-to-ligand redox-induced electron transfer (RIET). Chemical oxidation of complex 1 promotes the reduction of CoIII to CoII in compound 2 due to the redox-active nature of o-iminobenzoquinonate ligands. Remarkably, this is the first example of RIET in cobalt-based derivatives with this type of ligand. The oxidative states of the ligands and cobalt ion in both complexes were unequivocally established according to the X-ray data collection by using the utility of "metric oxidation state" (MOS). The spin states of the metal centers were unambiguously determined by density functional theory. The strong antiferromagnetic exchange via metal-ligand interactions is dominant in compounds 1 and 2, giving the doublet (S = 1/2) and triplet (S = 1) ground spin state, respectively.

6.
Inorg Chem ; 56(24): 14751-14754, 2017 Dec 18.
Artigo em Inglês | MEDLINE | ID: mdl-29185722

RESUMO

Iminopyridine modified by TEMPO nitroxide was utilized for the synthesis of an octahedral bis(o-semiquinonato)cobalt complex. Variable-temperature magnetic susceptibility measurements detect a valence tautomeric transformation in the temperature range 200-300 K. A reproducible hysteresis loop of about 40 K width is observed on the magnetic moment temperature dependence in the transition region. Differential scanning calorimetry measurements confirm different temperatures of phase transitions accompanying a valence-tautomeric transformation upon heating and cooling. Attempts to study the structural changes associated with the valence-tautomeric transformation by single-crystal X-ray diffraction failed because of the crystal destruction taking place upon cooling from 220 K. The powder X-ray diffraction pattern indicated an essential change of the unit cell upon cooling from 240 K.

7.
Inorg Chem ; 56(16): 9825-9833, 2017 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-28786665

RESUMO

The reaction of (dpp-Bian)EuII(dme)2 (3) (dpp-Bian is dianion of 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene; dme is 1,2-dimethoxyethane) with 2,2'-bipyridine (bipy) in toluene proceeds with replacement of the coordinated solvent molecules with neutral bipy ligands and affords europium(II) complex (dpp-Bian)EuII(bipy)2 (9). In contrast the reaction of related ytterbium complex (dpp-Bian)YbII(dme)2 (4) with bipy in dme proceeds with the electron transfer from the metal to bipy and results in (dpp-Bian)YbIII(bipy)(bipy-̇) (10) - ytterbium(III) derivative containing both neutral and radical-anionic bipy ligands. Noteworthy, in both cases dianionic dpp-Bian ligands retain its reduction state. The ligand-centered redox-process occurs when complex 3 reacts with N,N'-bis[2,4,6-trimethylphenyl]-1,4-diaza-1,3-butadiene (mes-dad). The reaction product (dpp-Bian)EuII(mes-dad)(dme) (11) consists of two different redox-active ligands both in the radical-anionic state. The reduction of 3,6-di-tert-butyl-4-(3,6-di-tert-butyl-2-ethoxyphenoxy)-2-ethoxycyclohexa-2,5-dienone (the dimer of 2-ethoxy-3,6-di-tert-butylphenoxy radical) with (dpp-Bian)EuII(dme)2 (3) caused oxidation of the dpp-Bian ligand to radical-anion to afford (dpp-Bian)(ArO)EuII(dme) (ArO = OC6H2-3,6-tBu2-2-OEt) (12). The molecular structures of complexes 9-12 have been established by the single crystal X-ray analysis. The magnetic behavior of newly prepared compounds has been investigated by the SQUID technique in the range 2-310 K. The isotropic exchange model has been adopted to describe quantitatively the magnetic properties of the exchange-coupled europium(II) complexes (11 and 12). The best-fit isotropic exchange parameters are in good agreement with their density functional theory-computed counterparts.

8.
Dalton Trans ; 46(34): 11440-11450, 2017 Aug 29.
Artigo em Inglês | MEDLINE | ID: mdl-28816308

RESUMO

A series of lanthanide(iii) complexes based on the new chiral ligand L, which contains 1,10-phenanthroline and (-)-menthol fragments, namely [LnL2(NO3)3] (Ln = Eu (1), Gd (2), Tb (3), Dy (4)), have been synthesized and structurally characterized. Complexes 1-4 are isostructural and crystallize in the non-centrosymmetric space group P41212. The mononuclear complexes comprise a 10-coordinate Ln3+ ion with two bidentate N,N-donor ligands (L) and three bidentate chelating nitrate groups. The magnetic properties of complexes 1-4 are determined mainly by the Ln3+ ions. In the case of complexes 3 and 4, significant anisotropy results in nonlinear field dependences of magnetization at low temperature. Complexes 1, 3 and 4 exhibit metal-centered red (Eu3+), green (Tb3+) and yellow (Dy3+) luminescence, respectively, whereas complex 2 displays blue ligand-based luminescence in the solid state at room temperature. The luminescence quantum yield for the solid samples increases in the order 4 < 2 ≈ 3 < 1. The europium(iii) complex shows long luminescence lifetimes (up to 1750 µs) and a very high quantum yield (φf = 0.87); these make this compound promising for application in sensing and optoelectronics.

9.
J Org Chem ; 82(15): 7764-7773, 2017 08 04.
Artigo em Inglês | MEDLINE | ID: mdl-28664730

RESUMO

The synthesis of four nitronyl nitroxide (NN) biradicals is described which are conjugatively linked through p-ter-phenyl (PPP), ter-thiophene (TTT) and alternating phenylene (P) and thiophene (T) units as PTP and TPT. We first utilized Suzuki and Stille coupling reactions through protection and deprotection protocols to synthesize these (NN) biradicals. Single crystals were efficiently grown for radical precursors of 3, 5, 6, PPP-NNSi, PTP-NNSi, and final biradicals of TTT-NN, TPT-NN, and PPP-NN, whose structures and molecular packing were examined by X-ray diffraction studies. As a result, much smaller torsions between the NN and thiophene units (∼10°) in TTT-NN and TPT-NN than for NN and phenyl units (∼29°) in PPP-NN were observed due to smaller hindrance for a five vs a six membered ring. All four biradicals TTT-NN, TPT-NN, PTP-NN, and PPP-NN were investigated by EPR and optical spectroscopy combined with DFT calculations. The magnetic susceptibility was studied by SQUID measurements for TTT-NN and TPT-NN. The intramolecular exchange interactions for TPT-NN and TTT-NN were found in good agreement with the ones calculated by broken symmetry DFT calculations.

10.
Dalton Trans ; 46(18): 5965-5975, 2017 May 09.
Artigo em Inglês | MEDLINE | ID: mdl-28425546

RESUMO

An unexpected substitution of the anionic chelating ligands at the MII centre by a neutral tripodal ligand has been observed in the reaction of MnII, CoII, NiII and CuII hexafluoroacetylacetonates (hfac) with tris(2-pyridyl)phosphine (Py3P) or its oxide (Py3P = O). The nature of the metal ion in M(hfac)2 and the M/L ratio determine the degree of substitution of hfac-anions (partial vs. total) and therefore, the structure of the complex formed (scorpionate vs. bis-scorpionate ones, respectively). Hence, the reaction of the ligands with [Cu(hfac)2(H2O)2] in an equimolar ratio affords scorpionate [Cu(N,N',N''-Py3P = X)(O,O'-hfac)(O-hfac)], wherein one hfac-ligand chelates metal, while the other hfac acts as an O-monodentate one. Using the two equivalents of Py3P in this reaction leads to [Cu(N,N',N''-Py3P)2](hfac)2, which contains a bis-scorpionate cation [Cu(Py3P)2]2+ and two noncoordinated hfac-anions. [Co(hfac)2(H2O)2] and [Ni(hfac)2(H2O)2], regardless of the M/L molar ratio, react with Py3P = O to give cationic scorpionates [M(N,N',N''-Py3P = O)(O,O'-hfac)(H2O)](hfac), in which one hfac-anion is noncoordinated. In contrast, [Mn(hfac)2(H2O)2], on interaction with Py3P, results in the cationic complex [Mn(N,N',N''-Py3P)2][Mn(hfac)3]2 bearing a bis-scorpionate cation [Mn(Py3P)2]2+ and two [Mn(hfac)3]2- counterions. The synthesized scorpionates have been characterized by X-ray diffractometry, cyclic voltammetry, SQUID magnetometry, FT-IR and UV-Vis techniques.

11.
J Org Chem ; 82(8): 4179-4185, 2017 04 21.
Artigo em Inglês | MEDLINE | ID: mdl-28358985

RESUMO

A 4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl (1) lithium derivative was found to react with perfluorobenzonitrile (2) substituting its para-fluorine atom to form 2-(4-cyanotetrafluorophenyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazol-3-oxide-1-oxyl (3), a new nitronyl nitroxide containing a multifunctional framework of strong electron-withdrawing nature. This result shows the possibility of obtaining multifunctional nitronyl nitroxides via the interaction of paramagnetic lithium derivatives as C-nucleophiles with polyfluoroarenes activated for nucleophilic substitution. The reaction regioselectivity is supported by the data of quantum-chemical calculations, which also show that the reaction follows a concerted pathway without formation of an intermediate. Reduction of nitronyl nitroxide 3 in system NaNO2-AcOH yielded corresponding iminonitroxide 4. Characterization of persistent radicals 3 and 4 obtained by the SNF synthetic strategy includes X-ray crystal structures, electron spin resonance data, and static magnetic-susceptibility measurements. X-ray diffraction analysis of both nitronyl nitroxide and iminonitroxide revealed a complete match of the parameters of their crystal lattices.

12.
Inorg Chem ; 56(5): 2426-2431, 2017 Mar 06.
Artigo em Inglês | MEDLINE | ID: mdl-28212027

RESUMO

A new bis(3,6-di-tert-butyl-catecholato)manganese complex with two 4-NIT-Py ligands was synthesized and characterized [4-NIT-Py = pyridine substituted at position 4 with nitronyl-nitroxide radical, 2-(pyridin-4-yl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl]. X-ray diffraction indicated an octahedral environment of the manganese atom with a trans arrangement of ligands. Bonds lengths in the inner coordination core of the metal and in the chelate cycles that are representative of the charge distribution between the metal and ligands displayed a Mn(IV)(Cat2-)2 charge distribution. Variable-temperature magnetic susceptibility measurements detected intramolecular ferromagnetic coupling between the Mn(IV) S = 3/2 spins and spins of nitronyl-nitroxyls and intermolecular ferromagnetic interactions of spins of adjacent nitronyl-nitroxide fragments in a chain of molecules at low temperatures. The last phenomenon is revealed by short contacts between nitronyl-nitroxide radicals of adjacent complex molecules.

13.
Chemistry ; 22(41): 14598-604, 2016 Oct 04.
Artigo em Inglês | MEDLINE | ID: mdl-27539325

RESUMO

It was shown that dipole-stabilized paramagnetic carbanion lithiated 4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazol-1-oxyl 3-oxide can be attached in a nucleophilic manner to either isolated or conjugated aldonitrones of the 2,5-dihydroimidazole 3-oxide and 2H-imidazole 1-oxide series to afford adducts the subsequent oxidation of which leads to polyfunctional mono- and diradicals. According to XRD, at least two polymorphic modifications can be formed during crystallization of the resulting paramagnetic compounds, and for each of them, geometric parameters of the molecules are similar. An EPR spectrum of the diradical in frozen toluene has a complicated lineshape, which can be fairly well reproduced by using X-ray diffraction structural analysis and the following set of parameters: D=14.9 mT, E=1.7 mT; tensor a((14) N)=[0.260 0.260 1.625] mT, two equivalent tensors for the nitronyl nitroxide moiety a((14) N)=[0.198 0.198 0.700] mT, and g≈2.007. According to our DFT and ab initio calculations, the intramolecular exchange in the diradical is very weak and most likely ferromagnetic.

14.
Inorg Chem ; 54(14): 6727-35, 2015 Jul 20.
Artigo em Inglês | MEDLINE | ID: mdl-26135029

RESUMO

Reaction of [ReOCl3(PPh3)2] with 3,5-di-tert-butyl-1,2-benzoquinone (3,5-DTBQ) in hot toluene produces a new complex [(3,5-di-tert-Bu2C6H2O2)Re(OPPh3)Cl3] (1), which was isolated and characterized by elemental analysis, IR, UV-vis spectroscopy, and cyclic voltammetry. In order to clarify the charge state of rhenium and the coordinated dioxolene ligand, X-ray experiments at 150 and 290 K were carried out. The C-O, C-C, and Re-O bond distances at both 150 and 290 K fall between those for semiquinolate (3,5-DTBSQ) and catecholate (3,5-DTBCat) forms; an empirical "metrical oxidation state" of the dioxolene ligand was estimated to be -1.5. High-level ab initio calculations (SOC-CASSCF/NEVPT2) revealed a mixed valence nature of the triplet ground state of complex 1 corresponding to a superposition of the Re(IV)-SQ and Re(V)-cat forms. In agreement with the high-level ab initio and DFT calculations, the temperature dependence of the magnetic susceptibility (5-300 K) is well described in the assumption of the triplet ground state, with the anomalously large zero-field splitting (ZFS) arising from the spin-orbit coupling. According to the ab initio calculations, all absorption bands in the visible region of the electronic absorptions spectrum are assigned to the LMCT bands, with significant contribution of the intraligand transition in the most intense band at 555 nm.


Assuntos
Benzoquinonas/química , Complexos de Coordenação/química , Rênio/química , Cristalografia por Raios X , Modelos Moleculares , Teoria Quântica
15.
Inorg Chem ; 54(13): 6090-9, 2015 Jul 06.
Artigo em Inglês | MEDLINE | ID: mdl-26052864

RESUMO

A number of pentacoordinated gallium complexes iSQ2GaR (1-7) (R = Et (1), Me (2), N3 (3), Cl (4), Br (5), I (6), NCS (7)) where iSQ is a radical anion of 4,6-di-tert-butyl-N-(2,6-diisopropylphenyl)-o-iminobenzoquinone were synthesized, and crystalline samples of 1-7 were characterized using magnetic susceptibility measurements. The character of magnetic exchange interaction between spins of o-iminosemiquinonate radicals was found to be strongly influenced by the nature of the apical substituent. The antiferromagnetic coupling is predominant when the apical position is occupied by halogens or other tested inorganic anions, and the value of exchange interaction parameter varies from -99 to -176 K for R = I and NCS, respectively. In the case of alkyl groups the ferromagnetic exchange prevails and, as the result, the triplet ground state for pentacoordianted biradical compounds was observed. Compounds 1-7 demonstrate a biradical X-band EPR spectrum in frozen toluene matrix. The molecular structures of 4, 6, and 7 have been established by single-crystal X-ray analysis. A computational DFT UB3LYP/6-31G(d,p) study was performed on complexes 1-7 in order to understand the reason for changes in the magnetic behavior of the related diradical gallium compounds. The calculations showed that the magnetic behavior of the complexes with inorganic anions is conditioned by the presence of antiferromagnetic exchange channel formed as a consequence of overlapping between donor atomic orbitals of iminoquinone with π-orbitals of halogen atoms (4-6) or nitrogen atom (3, 7).

16.
Inorg Chem ; 54(13): 6078-80, 2015 Jul 06.
Artigo em Inglês | MEDLINE | ID: mdl-26107184

RESUMO

Two novel heteroligand o-semiquinonato-formazanato cobalt complexes [Co(3,6-SQ)(Form)] (1) and [Co(3,6-SQ)2(Form)] (2) (3,6-SQ is 3,6-di-tert-butyl-o-benzosemiquinonate radical anion; Form is 1,3,5-triphenylformazanate anion) were synthesized and characterized in detail. The molecular structures of [Co(3,6-SQ)(Form)] and [Co(3,6-SQ)2(Form)] were determined by X-ray analysis. Magnetic susceptibility measurements and spectroscopic studies have shown that square-planar complex 1 is diamagnetic with a residual paramagnetism due to antiferromagnetic exchange metal-ligand. Complex 2 includes cobalt(III) in the low-spin state and two anionic-radical o-semiquinonato and one formazanate ligand.

17.
Inorg Chem ; 54(14): 7007-13, 2015 Jul 20.
Artigo em Inglês | MEDLINE | ID: mdl-26121418

RESUMO

Low-temperature interaction of [1,2,5]thiadiazolo[3,4-c][1,2,5]thiadiazole (1) with MoMes2 (Mes = mesitylene/1,3,5-trimethylbenzene) in tetrahydrofuran gave the heterospin (S1 = S2 = (1)/2) radical-ion salt [MoMes2](+)[1](-) (2) whose structure was confirmed by single-crystal X-ray diffraction (XRD). The structure revealed alternating layers of the cations and anions with the Mes ligands perpendicular, and the anions tilted by 45°, to the layer plane. At 300 K the effective magnetic moment of 2 is equal to 2.40 µB (theoretically expected 2.45 µB) and monotonically decreases with lowering of the temperature. In the temperature range 2-300 K, the molar magnetic susceptibility of 2 is well-described by the Curie-Weiss law with parameters C and θ equal to 0.78 cm(3) K mol(-1) and -31.2 K, respectively. Overall, the magnetic behavior of 2 is similar to that of [CrTol2](+)[1](-) and [CrCp*2](+)[1](-), i.e., changing the cation [MAr2](+) 3d atom M = Cr (Z = 24) with weak spin-orbit coupling (SOC) to a 4d atom M = Mo (Z = 42) with stronger SOC does not affect macroscopic magnetic properties of the salts. For the XRD structure of salt 2, parameters of the Heisenberg spin-Hamiltonian were calculated using the broken-symmetry DFT and CASSCF approaches, and the complex 3D magnetic structure with both the ferromagnetic (FM) and antiferromagnetic (AF) exchange interactions was revealed with the latter as dominating. Salt 2 is thermally unstable and slowly loses the Mes ligands upon storage at ambient temperature. Under the same reaction conditions, interaction of 1 with MoTol2 (Tol = toluene) proceeded with partial loss of the Tol ligands to afford diamagnetic product.

18.
Dalton Trans ; 44(12): 5727-34, 2015 Mar 28.
Artigo em Inglês | MEDLINE | ID: mdl-25711776

RESUMO

New tetranuclear heteroleptic complexes [Er4(dbm)6(O-btd)4(OH)2] (1) and [Er4(dbm)4(O-btd)6(OH)2] (2) (O-btd = 4-hydroxo-2,1,3-benzothiadiazolate and dbm = dibenzoylmethanide) and their solvates with toluene, THF and CH2Cl2 were prepared using two synthetic approaches. The structures of the products were confirmed by single-crystal X-ray diffraction. Magnetic properties of 1 and 2 are in good agreement with X-ray data. The effective magnetic moment (µeff) values at 300 K for 1 and 2 corresponds to a system of 4 non-interacting Er(III) ions in the ground state 4J15/2 with g = 6/5. At ambient temperature and upon excitation with λexc = 450 nm, complexes 1 and 2 exhibit luminescence at 1530 nm, i.e. in the near infra-red (NIR) region. The luminescence intensity grows with increasing the number of the (O-btd)− ligands in the complexes. This observation suggests (O-btd)− as a new efficient antenna ligand for the lanthanide-based NIR luminescence.


Assuntos
Chalconas/química , Complexos de Coordenação/química , Érbio/química , Substâncias Luminescentes/química , Tiadiazóis/química , Chalconas/síntese química , Complexos de Coordenação/síntese química , Ligantes , Luminescência , Substâncias Luminescentes/síntese química , Imãs/química , Modelos Moleculares , Tiadiazóis/síntese química , Difração de Raios X
19.
Chem Sci ; 6(1): 497-504, 2015 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-28936305

RESUMO

One-electron oxidation of two series of diaryldichalcogenides (C6F5E)2 (13a-c) and (2,6-Mes2C6H3E)2 (16a-c) was studied (E = S, Se, Te). The reaction of 13a and 13b with AsF5 and SbF5 gave rise to the formation of thermally unstable radical cations [(C6F5S)2]˙+ (14a) and [(C6F5Se)2]˙+ (14b) that were isolated as [Sb2F11]- and [As2F11]- salts, respectively. The reaction of 13c with AsF5 afforded only the product of a Te-C bond cleavage, namely the previously known dication [Te4]2+ that was isolated as [AsF6]- salt. The reaction of (2,6-Mes2C6H3E)2 (16a-c) with [NO][SbF6] provided the corresponding radical cations [(2,6-Mes2C6H3E)2]˙+ (17a-c; E = S, Se, Te) in the form of thermally stable [SbF6]- salts in nearly quantitative yields. The electronic and structural properties of these radical cations were probed by X-ray diffraction analysis, EPR spectroscopy, and density functional theory calculations and other methods.

20.
Dalton Trans ; 43(48): 18104-16, 2014 Dec 28.
Artigo em Inglês | MEDLINE | ID: mdl-25355381

RESUMO

Heterobimetallic complexes [SmTb(piv)6(phen)2] (1), [SmTb(piv)6(bath)2]·1.75EtOH (2a·1.75EtOH), [SmTb(piv)6(bath)2]·2EtOH (2b·2EtOH), and [SmTb(piv)6(bath)2]·EtOH (2b·EtOH), where piv is (CH3)3CCO2(-), phen is 1,10-phenanthroline, and bath is 4,7-diphenyl-1,10-phenanthroline, were synthesized and studied by X-ray diffraction. It was shown that complexes 2a·1.75EtOH and 2b·2EtOH have different molecular and crystal structures. Complexes 2a·1.75EtOH, 2b·2EtOH, and 2b·EtOH differ in the structural functions of µ2-piv anions. 2a·1.75EtOH contains two µ2-piv-κ(2)O,O' anions and two µ2-piv-κ(2)O,O,O' anions, whereas 2b·2EtOH and 2b·EtOH have four µ2-piv-κ(2)O,O' anions. According to the mass spectrometry data, the dimeric molecule [SmTb(piv)6] is the major metal-containing component of gas-phase complexes 1, 2a·1.75EtOH, and 2b·2EtOH. The characteristic features of the thermal behavior of these complexes were revealed, and their magnetic and photoluminescence (PL) properties were investigated. A unique feature of desolvated complexes 2a·1.75EtOH and 2b·2EtOH is melting at high temperatures before thermal decomposition. The magnetic properties of 1 and 2a·1.75EtOH are determined mainly by the Tb(3+) ions. The optical properties of these complexes and their homodinuclear analogs were analyzed by photoluminescence, excitation, phosphorescence, and scattering spectroscopy and by lifetime measurements at 77 K and 300 K. As the temperature decreases to 77 K, the PL intensity of Tb(3+) ions in 1 and 2a·1.75EtOH substantially increases by 40 and 100 times, respectively, compared to 300 K. The PL color evidently changes from red at 300 K to bright green at 77 K. Based on these results, the mechanism of intramolecular energy transfer between the ligand levels and Sm(3+) and Tb(3+) ions under UV radiation was proposed.

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