A Multi-Redox Responsive Cyanometalate-Based Metallogel.

A TTF-based (TTF=tetrathiafulvalene) tridentate ligand (α-(4'-methyl-4,5-di-n-dodecylthylthiotetrathiafulvalene-5'-ylthio)- α'-[2,2,2-tris(1-pyrazolyl)ethoxy]-p-xylene) (L) with long-chain alkyl moieties was prepared in order to obtain a new multi-redox active gelator based on a mixed-metal octanuclear complex [FeIII4 NiII4 (CN)12 (tp)4 (L)4 ](BF4 )4 (1). The magnetism, electrochemistry, and gelation behavior of 1 were studied and 1,2-dichlorobenzene solutions of 1 are shown to display thermoreversible gelation behavior at room temperature. Furthermore, the gel phase of 1 was shown to undergo room-temperature gel-to-sol transformations induced by both the oxidation and reduction of the gelator complex by F4 TCNQ or [FeII (Cp*)2 ], respectively.

Lability-controlled syntheses of heterometallic clusters.

A bulky bidentate ligand was used to stabilize a macrocyclic [Fe(III)8Co(II)6] cluster. Tuning the basicity of the ligand by derivatization with one or two methoxy groups led to the isolation of a homologous [Fe(III)8Co(II)6] species and a [Fe(III)6Fe(II)2Co(III)2Co(II)2] complex, respectively. Lowering the reaction temperatures allowed isolation of [Fe(III)6Fe(II)2Co(III)2Co(II)2] clusters with all three ligands. Temperature-dependent absorption data and corresponding experiments with iron/nickel systems indicated that the iron/cobalt self-assembly process was directed by the occurrence of solution-state electron-transfer-coupled spin transition (ETCST) and its influence on reaction intermediate lability.

Multiredox active [3 × 3] copper grids.

A nonanuclear copper grid complex, [Cu(II)9(L)6](BF4)6·1-PrOH·5H2O (1·1-PrOH·5H2O; L = 2,6-bis[5-(2-pyridinyl)-1H-pyrazol-3-yl]pyridine), was synthesized with a [3 × 3] grid structure consisting of nine Cu(II) ions and six deprotonated ligands and displayed four-step quasi-reversible redox behavior from [Cu(II)9] to [Cu(I)4Cu(II)5]. The corresponding heterovalent complex [Cu(I)2Cu(II)7(L)6](PF6)4·3H2O (2·3H2O) was successfully isolated and had a distorted core structure that radically changed the intramolecular magnetic coupling pathways.

Cyanide-bridged [Fe8M6] clusters displaying single-molecule magnetism (M=Ni) and electron-transfer-coupled spin transitions (M=Co).

Cyanide-bridged metal complexes of [Fe(8)M(6)(µ-CN)(14)(CN)(10)(tp)(8)(HL)(10)(CH(3)CN)(2)][PF(6)](4)⋅n CH(3)CN⋅m H(2)O (HL=3-(2-pyridyl)-5-[4-(diphenylamino)phenyl]-1H-pyrazole), tp(-) =hydrotris(pyrazolylborate), 1: M=Ni with n=11 and m=7, and 2: M=Co with n=14 and m=5) were prepared. Complexes 1 and 2 are isomorphous, and crystallized in the monoclinic space group P2(1)/n. They have tetradecanuclear cores composed of eight low-spin (LS) Fe(III) and six high-spin (HS) M(II) ions (M=Ni and Co), all of which are bridged by cyanide ions, to form a crown-like core structure. Magnetic susceptibility measurements revealed that intramolecular ferro- and antiferromagnetic interactions are operative in 1 and in a fresh sample of 2, respectively. Ac magnetic susceptibility measurements of 1 showed frequency-dependent in- and out-of-phase signals, characteristic of single-molecule magnetism (SMM), while desolvated samples of 2 showed thermal- and photoinduced intramolecular electron-transfer-coupled spin transition (ETCST) between the [(LS-Fe(II))(3) (LS-Fe(III))(5)(HS-Co(II))(3)(LS-Co(III))(3)] and the [(LS-Fe(III))(8)(HS-Co(II))(6)] states.

Encapsulation controlled single molecule magnetism in tetrathiafulvalene-capped cyanide-bridged cubes.

New TTF-based (TTF = tetrathiafulvalene) ligands, L1 and L2 (L1 = α-(4'-methyl-4,5-ethylenedithiotetrathiafulvalene-5'-thio)-α'-[tris-2,2,2-(1-pyrazolyl)ethoxy]-p-xylene and L2 = α-(4'-methyl-4,5-dimethylthiotetrathiafulvalene-5'-thio)-α'-[tris-2,2,2-(1-pyrazolyl)ethoxy]-p-xylene), possessing tris-pyrazolyl coordination sites, were synthesized. The reactions of Ni(BF(4))(2)·6H(2)O with the TTF-ligands (L1 and L2), n-Bu(4)N[Fe(CN)(3)(tp or pztp)] (tp = hydrotris(pyrazol-1-yl)borate and pztp = tetrakis(pyrazol-1-yl)borate) in the presence of additional counter ions afforded two cyanide-bridged octanuclear complexes: [Fe(III)(4)Ni(II)(4)(CN)(12)(pztp)(4)(L1)(4)](BF(4))(4) (1) and [Fe(III)(4)Ni(II)(4)(CN)(12)(pztp)(4)(L2)(4)](PF(6))(4) (2). Using a similar procedure to that employed in the synthesis of complex 2, with the addition of sodium tetraphenylborate, yielded a two-electron-reduced compound, Na[Fe(III)(2)Fe(II)(2)Ni(II)(4)(CN)(12)(tp)(4)(L2)(4)](BF(4))(3) (3), in which a sodium ion was encapsulated by the cube. The host-guest complex 3 showed enhanced redox behaviour and while magnetic susceptibility measurements revealed ferromagnetic interactions to be operative in all three complexes, the cation encapsulation behaviour of 3 led it to exhibit single molecule magnet-type properties.