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1.
Chemistry ; 25(65): 14858-14869, 2019 Nov 22.
Artigo em Inglês | MEDLINE | ID: mdl-31523861

RESUMO

A series of compounds with Sc3 N@Ih -C80 in the neutral, monomeric, and dimeric anion states have been prepared in the crystalline form and their molecular structures and optical and magnetic properties have been studied. The neutral Sc3 N@Ih -C80 ⋅3 C6 H4 Cl2 (1) and (Sc3 N@Ih -C80 )3 (TPC)2 ⋅5 C6 H4 Cl2 (2, TPC=triptycene) compounds both crystallized in a high-symmetry trigonal structure. The reduction of Sc3 N@Ih -C80 to the radical anion resulted in dimerization to form diamagnetic singly bonded (Sc3 N@Ih -C80 - )2 dimers. In contrast to {[2.2.2]cryptand(Na+ )}2 (Sc3 N@Ih -C80 - )2 ⋅2.5 C6 H4 Cl2 (3) with strongly disordered components, we synthesized new dimeric phases {[2.2.2]cryptand- (K+ )}2 (Sc3 N@Ih -C80 - )2 ⋅2 C6 H4 Cl2 (4) and {[2.2.2]cryptand- (Cs+ )}2 (Sc3 N@Ih -C80 - )2 ⋅2 C6 H4 Cl2 (5) in which only one major dimer orientation was found. The thermal stability of the (Sc3 N@Ih -C80 - )2 dimers was studied by EPR analysis of 3 to show their dissociation in the 400-460 K range producing monomeric Sc3 N@Ih -C80 .- radical anions. This species shows an EPR signal with a hyperfine splitting of 5.8 mT. The energy of the intercage C-C bond was estimated to be 234±7 kJ mol-1 , the highest value among negatively charged fullerene dimers. The EPR spectra of crystalline (Bu3 MeP+ )3 (Sc3 N@Ih -C80 .- )3 ⋅C6 H4 Cl2 (6) are presented for the first time. The salt shows an asymmetric EPR signal, which could be fitted by three lines. Two lines were attributed to Sc3 N@Ih -C80 .- . Hyperfine splitting is manifested above 180 K due to the hyperfine interaction of the electron spin with the three scandium atoms (a total of 22 lines with an average splitting of 5.32 mT are observed at 220 K). Furthermore, each of the 22 lines is additionally split into six lines with an average separation of 0.82 mT. The large splitting indicates intrinsic charge and spin density transfer from the fullerene cage to the Sc3 N cluster. Both the monomeric and dimeric Sc3 N@Ih -C80 - anions show an intrinsic shift of the IR bands attributed to the Sc3 N cluster and new bands corresponding to these species appear in the NIR range of their UV/Vis/NIR spectra, which allows these anions to be distinguished from neutral species.

2.
Chemistry ; 25(64): 14583-14597, 2019 Nov 18.
Artigo em Inglês | MEDLINE | ID: mdl-31361924

RESUMO

Reactions of [Mn(H2 dapsc)Cl2 ]⋅H2 O (dapsc=2,6- diacetylpyridine bis(semicarbazone)) with K3 [Fe(CN)6 ] and (PPh4 )3 [Fe(CN)6 ] lead to the formation of the chain polymeric complex {[Mn(H2 dapsc)][Fe(CN)6 ][K(H2 O)3.5 ]}n ⋅1.5n H2 O (1) and the discrete pentanuclear complex {[Mn(H2 dapsc)]3 [Fe(CN)6 ]2 (H2 O)2 }⋅4 CH3 OH⋅3.4 H2 O (2), respectively. In the crystal structure of 1 the high-spin [MnII (H2 dapsc)]2+ cations and low-spin hexacyanoferrate(III) anions are assembled into alternating heterometallic cyano-bridged chains. The K+ ions are located between the chains and are coordinated by oxygen atoms of the H2 dapsc ligand and water molecules. The magnetic structure of 1 is built from ferrimagnetic chains, which are antiferromagnetically coupled. The complex exhibits metamagnetism and frequency-dependent ac magnetic susceptibility, indicating single-chain magnetic behavior with a Mydosh-parameter φ=0.12 and an effective energy barrier (Ueff /kB ) of 36.0 K with τ0 =2.34×10-11  s for the spin relaxation. Detailed theoretical analysis showed highly anisotropic intra-chain spin coupling between [FeIII (CN)6 ]3- and [MnII (H2 dapsc)]2+ units resulting from orbital degeneracy and unquenched orbital momentum of [FeIII (CN)6 ]3- complexes. The origin of the metamagnetic transition is discussed in terms of strong magnetic anisotropy and weak AF interchain spin coupling.

3.
Dalton Trans ; 48(25): 9328-9336, 2019 Jun 25.
Artigo em Inglês | MEDLINE | ID: mdl-31166344

RESUMO

The iron(iii) complex [Fe(Hsemsal)(semsal)]·3H2O (1) (H2semsal - salicylaldehyde semicarbazone) has been synthesized and characterized by powder and single crystal X-ray diffraction, and magnetic susceptibility measurements. Crystal structure analysis showed that the complex forms neat stacks stabilized by hydrogen-bonding through water molecules and π-π interactions between phenolate rings of ligands. The complex does not exhibit spin-crossover phenomena and remains in the high-spin state down to 2 K. DFT calculations were performed for a series of neutral Fe(iii) complexes, and the influence of the N2S2O2, N2Se2O2 and N2O4 coordination environment on the spin transition in these complexes was traced. The effect of substituents in the benzene ring of salicylaldehyde on the stabilization of the HS or LS states in complexes of this type was analyzed.

4.
Inorg Chem ; 57(2): 583-589, 2018 Jan 16.
Artigo em Inglês | MEDLINE | ID: mdl-29278502

RESUMO

A diamagnetic complex, {(cis-indigo-N,N)2-(Cp*IrIII)} (1), in which deprotonated cis-indigo dianions coordinate an iridium center through two nitrogen atoms was obtained. By employment of the ability of the iridium center in 1 to coordinate an additional ligand, the complex [(Bu4N+)2{[SnII(Pc•3-)](cis-indigo-N,N)2-Cp*IrIII}•-2·0.5(H2Indigo)·2.5C6H4Cl2 (2), which has two functional ligands coordinating an IrIII center, was obtained. This complex has a magnetic moment of 1.71 µB at 300 K, in accordance with an S = 1/2 spin state. The spin density is mainly delocalized over the Pc•3- macrocycle and partially on (cis-indigo-N,N)2-. Due to an effective π-π interaction, a thermally activated charge transfer from [SnII(Pc•3-)]•- to (cis-indigo-N,N)2- is observed, with an estimated Gibbs energy (-ΔG°) of 9.27 ± 0.18 kJ/mol. The deprotonation of indigo associated with the coordination of IrIII by the indigo releases H+ ions, which protonate noncoordinating indigo molecules to produce leuco cis-indigo (H2Indigo). One H2indigo links two (cis-indigo-N,N)2- dianions in 2 to produce strong N-H···O═C and O-H···O═C hydrogen-bonding interactions.

5.
Inorg Chem ; 56(15): 8926-8943, 2017 Aug 07.
Artigo em Inglês | MEDLINE | ID: mdl-28686422

RESUMO

Two one-dimensional cyano-bridged coordination polymers, namely, {[MnII(dapsc)][MnIII(CN)6][K(H2O)2.75(MeOH)0.5]}n·0.5n(H2O) (I) and {[MnII(dapsc)][MnIII(CN)6][K(H2O)2(MeOH)2]}n (II), based on alternating high-spin MnII(dapsc) (dapsc = 2,6-diacetylpyridine bis(semicarbazone)) complexes and low-spin orbitally degenerate hexacyanomanganate(III) complexes were synthesized and characterized structurally and magnetically. Static and dynamic magnetic measurements reveal a single-chain magnet (SCM) behavior of I with an energy barrier of Ueff ≈ 40 K. Magnetic properties of I are analyzed in detail in terms of a microscopic theory. It is shown that compound I refers to a peculiar case of SCM that does not fall into the usual Ising and Heisenberg limits due to unconventional character of the MnIII-CN-MnII spin coupling resulting from a nonmagnetic singlet ground state of orbitally degenerate complexes [MnIII(CN)6]3-. The prospects of [MnIII(CN)6]3- complex as magnetically anisotropic molecular building block for engineering molecular magnets are critically analyzed.

6.
Chem Commun (Camb) ; 52(71): 10763-6, 2016 Sep 14.
Artigo em Inglês | MEDLINE | ID: mdl-27511304

RESUMO

Reduction of scandium nitride clusterfullerene, Sc3N@Ih-C80, by sodium fluorenone ketyl in the presence of cryptand[2,2,2] allows the crystallization of the {cryptand[2,2,2](Na(+))}2(Sc3N@Ih-C80(-))2·2.5C6H4Cl2 (1) salt. The Sc3N@Ih-C80˙(-) radical anions are dimerized to form single-bonded (Sc3N@Ih-C80(-))2 dimers.

7.
Inorg Chem ; 55(17): 9121-30, 2016 Sep 06.
Artigo em Inglês | MEDLINE | ID: mdl-27541570

RESUMO

The radical anion salt [Fe{HC(pz)3}2](TCNQ)3 demonstrates conductivity and spin-crossover (SCO) transition associated with Fe(II) complex cation subsystem. It was synthesized and structurally characterized at temperatures 100, 300, 400, and 450 K. The compound demonstrates unusual for 7,7,8,8,-tetracyanoquinodimethane (TCNQ)-based salts quasi-two-dimensional conductivity. Pronounced changes of the in-plane direct-current resistivity and intensity of the electron paramagnetic resonance (EPR) signal, originated from TCNQ subsystem, precede the SCO transition at the midpoint T* = 445 K. The boltzmannian growth of the total magnetic response and structural changes in the vicinity of T* uniquely show that half [Fe{HC(pz)3}2] cations exist in high-spin state. Robust broadening of the EPR signal triggered by the SCO transition is interpreted in terms of cross relaxation between the TCNQ and Fe(II) spin subsystems.

8.
Dalton Trans ; 42(19): 6810-6, 2013 May 21.
Artigo em Inglês | MEDLINE | ID: mdl-23483056

RESUMO

Ionic compounds containing radical anions of metal-free phthalocyanine (H2Pc˙(-)): (H2Pc˙(-))(cryptand[2,2,2][Na(+)])·1.5C6H4Cl2 (1) and (H2Pc˙(-))(TOA(+))·C6H4Cl2 (2) have been obtained as single crystals for the first time. Their crystal structures have been determined, and optical and magnetic properties have been investigated. The H2Pc˙(-) radical anions have a slightly bowl-like shape with four pyrrole nitrogen atoms located below the molecular plane, while four phenylene substituents are located above this plane. Changes in the average length of N-C and C-C bonds in H2Pc˙(-) in comparison with those in neutral H2Pc indicate that negative charge is mainly delocalized over the 24-atom phthalocyanine ring rather than the phenylene substituents. The H2Pc˙(-) formation is accompanied by a shift of up to 10 cm(-1) and disappearance of some intense IR-active bands whereas the band of the N-H stretching mode is shifted by 21-27 cm(-1) to larger wavenumbers. New bands attributed to H2Pc˙(-) appear in the NIR spectra of the salts with maxima at 1033 and 1028 nm for 1 and 2, respectively. The formation of H2Pc˙(-) is accompanied by the splitting of the Soret and Q-bands of H2Pc into several bands and their blue-shift up to 32 nm. Narrow EPR signals with g = 2.0033 and linewidth of 0.16-0.24 mT at room temperature in the spectra of the salts were attributed to the H2Pc˙(-) radical anions. According to SQUID measurements they have S = 1/2 spin states with effective magnetic moments of 1.73 (1) and 1.78 (2) µB at 300 K. Magnetic behavior of 1 and 2 follows the Curie-Weiss law with negative Weiss temperatures of -0.9 and -0.5 K, respectively, indicating weak antiferromagnetic interactions of spins. The EPR signal splits into two lines below 120 and 80 K for 1 and 2, respectively and these lines are noticeably broadened below 25 K.

9.
Dalton Trans ; 41(30): 9170-5, 2012 Aug 14.
Artigo em Inglês | MEDLINE | ID: mdl-22653268

RESUMO

Ionic complexes containing µ(2)-hydroxo-bonded (MgPc)(2)OH(-) phthalocyanine assemblies and C(60)(-) anions: {(MgPc)(2)OH(-)}(2)·(C(60)(-))(2)·(PMDAE(+))(4)·(C(6)H(5)CN)(4) (1); {(MgPc)(2)OH(-)}(2)·(C(60)(-))(2)·(TMP(+))(4)·(C(6)H(5)CN)(3)·(C(6)H(4)Cl(2))(2.5) (2) (where PMDAE(+) is the cation of N,N,N',N',N'-pentamethyldiaminoethane and TMP(+) is the N,N'N'-trimethylpiperazinium cation) have been obtained as single crystals. The ionic ground state of the complexes is justified by the EPR spectra and the spectra in the IR and NIR ranges. The C(60)˙(-) radical anions are dimerized both in 1 and 2 in the 240-220 K range. Dimerization is accompanied by the reversible transition of the complexes from paramagnetic to diamagnetic state. MgPc forms unusual (MgPc)(2)OH(-) assemblies, in which the hydroxo-anion coordinates to two MgPc molecules by a µ(2)-fashion. The length of the Mg-O bonds is 1.936-1.955(2) Å, the Mg-O-Mg angle is 133.37-135.27(4)° and the displacement of the Mg atoms out of the mean 24-atom phthalocyanine plane is 0.77-0.86 Å. The packing of spherical fullerene and planar phthalocyanine molecules is attained in a crystal by the insertion of fullerenes between phenylene groups of phthalocyanines. It has been shown that metal phthalocyanines in ionic complexes with C(60) form M(II)Pc·(L(-)) assemblies, whereas metalloporphyrins form M(II)porphyrin·(C(+)) assemblies.

10.
Chem Commun (Camb) ; (19): 2194-6, 2008 May 21.
Artigo em Inglês | MEDLINE | ID: mdl-18463737

RESUMO

Complementary shapes of the neutral symmetrical halogen-bond bis-donor core and octahedral inorganic cluster core prevent halogen-bonded polymers developing in more than one direction, favouring further templating by conducting radical cation slabs and yielding an 8 : 1 : 1 phase formulation instead of n : 2 : 1, with a 2D net, or m : 3 : 1, with a pseudo-cubic architecture, which may in principle also be targeted.

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