Spin crossover of ferric complexes with catecholate derivatives. Single-crystal X-ray structure, magnetic and Mössbauer investigations.

Complexes of general formula [(TPA)Fe(R-Cat)]X.nS were synthesised with different catecholate derivatives and anions (TPA = tris(2-pyridylmethyl)amine, R-Cat2- = 4,5-(NO2)2-Cat2- denoted DNC(2-); 3,4,5,6-Cl4-Cat2- denoted TCC2-; 3-OMe-Cat(2-); 4-Me-Cat(2-) and X = BPh4-; NO3-; PF6-; ClO4-; S = solvent molecule). Their magnetic behaviours in the solid state show a general feature along the series, viz., the occurrence of a thermally-induced spin crossover process. The transition curves are continuous with transition temperatures ranging from ca. 84 to 257 K. The crystal structures of [(TPA)Fe(DNC)]X (X = PF6-; BPh4-) and [(TPA)Fe(TCC)]X.nS (X = PF6-; NO3- and n= 1, S = H2O; ClO4- and n= 1, S = H2O; BPh4- and n= 1, S = C3H6O) were solved at 100 (or 123 K) and 293 K. For those two systems, the characteristics of the [FeN(4)O(2)] coordination core and those of the dioxolene ligands appear to be consistent with a prevailing Fe(III)-catecholate formulation. This feature is in contrast with the large quantum mixing between Fe(III)-catecholate and Fe(II)-semiquinonate forms recently observed with the more electron donating simple catecholate dianion. The thermal spin crossover process is accompanied by significant changes of the molecular structures as shown by the average variation of the metal-ligand bond distances which can be extrapolated for a complete spin conversion from ca. 0.123 to 0.156 A. The different space groups were retained in the low- and high-temperature phases.

Methoxy-ether and crown-ether derivatives of tetrahomodioxa- and octahomotetraoxacalix[4]arenes.

Three methoxy-ether and one methoxy-ether/crown-ether derivatives of p-tert-butyltetrahomodioxa- and p-R-octahomotetraoxacalix[4]arenes (R = methyl, tert-butyl, H) have been investigated. The first three compounds, 7,15,21,27-tetra-tert-butyl-29,30,31,32-tetramethoxy-3,11-dioxapentacyclo[23.3.1.1(5,9).1(13,17).1(19,23)]ditriaconta-1(29),5,7,9(30),13,15,-17(31),19,21,23(32),25,27-dodecaene, C(50)H(68)O(6), 33,34,35,36-tetramethoxy-7,15,23,31-tetramethyl-3,11,19,27-tetraoxapentacyclo[27.3.1.1(5,9).1(13,17).1(21,25)]hexatriaconta-1(33),5,7,9(34),13,15,17(35),21,23,25(36),29,31-dodecaene, C(40)H(48)O(8), and 7,23-di-tert-butyl-33,34,35,36-tetramethoxy-3,11,19,27-tetraoxapentacyclo[27.3.1.1(5,9).1(13,17).1(21,25)]hexatriaconta-1(33),5,7,9(34),13,15,17(35),- 21,23,25(36),29,31-dodecaene, C(44)H(56)O(8), in the partial-cone or 1,2-alternate conformations, present the common feature of methoxy-ether self-inclusion, while the fourth, 42,43-dimethoxy-7,15,23,31-tetramethyl-3,11,19,27,34,37,40-heptaoxahexacyclo[15.15.9.1(5,9).1(21,25).0(13,41).0(29,33)]tritetraconta-5(42),6,8,13(41),14,16,21(43),22,24,29(33),30,32-dodecaene, C(42)H(50)O(9), adopts the 1,3-alternate conformation owing to the presence of a 1,3-polyether chain.

p-methyltetrahomodioxacalix[4]arene.

The title compound, 7,13,21,27-tetramethyl-3,17-dioxapentacyclo[23.3.1.1(5,9).1(11,15).1(9,23)]ditriaconta-1(29),5,7,9(30),11(31),-12,14,19(32),20,22,25,27-dodecaene-29,30,31,32-tetraol, C34H36O6, assumes in the solid state a very distorted cone-like conformation stabilized by intramolecular simple and bifurcated hydrogen bonds involving both phenolic and ether O atoms. One part of the molecule, comprising an ether link, is included in the cavity of an adjacent calixarene related by a screw axis, giving rise to a one-dimensional self-inclusion polymer.

An ion pair uniting a gadolinium(III)-Schiff base complex and uranyl tetrachloride.

The Schiff base N-(tert-butyl)-3-methoxysalicylaldimine (LH) forms a complex with gadolinium(III) chloride, [GdCl(2)(LH)(2)(C(5)H(5)N)(2)](+), in which the two O atoms of each ligand are coordinated (the phenolic O atom being deprotonated) and the imine N atom is protonated and involved in a hydrogen bond with the phenoxide group. This complex crystallizes as an ion pair with uranyl tetrachloride, i.e. bis(bis[2-(tert-butyliminiomethyl)-6-methoxyphenolato-O,O']dichlorobis(pyridine-N)gadolinium(III)) tetrachlorodioxouranium(VI) tetrapyridine solvate [GdCl(2)(C(12)H(17)NO(2))(2)(C(5)H(5)N)(2)](2)[UCl(4)O(2)].4C(5)H(5)N. The U atom of the UCl(4)O(2) anion lies on an inversion centre.

Crystallographic, X-ray absorption, and IR studies of solid- and solution-state structures of tris(nitrato) N,N,N',N'-tetraethylmalonamide complexes of lanthanides. Comparison with the Americium complex.

To fine-tune the design of optimized donor ligands for nuclear waste actinide selective extraction, both electronic and molecular structures of the actinide complexes that are formed must be investigated. In particular, to achieve the selective complexation of transplutonium 3+ ions versus lanthanide 3+ ions is one of the major challenges, given the chemical similarities between these two f-element families. In this work, the structure of solvent-phase M(NO3)3(TEMA)2 complexes (Ln = Nd, Eu, Ho, Yb, Lu, Am; TEMA = N,N,N',N'-tetraethylmalonamide) was investigated by liquid-phase spectroscopic methods among which extended X-ray absorption fine structure played a major role. In addition, the crystal structures of the species Nd(NO3)3(TEMA)2 and Yb(NO3)3(TEMA)2 have been determined by X-ray diffraction. Nd(NO3)3(C11N2O2H22)2 crystallizes in the monoclinic system (P2(1) space group; a = 11.2627(4) A, b = 20.5992(8) A, c = 22.2126(8) A; alpha = gamma = 90 degrees, beta = 102.572(1) degrees; Z = 6), and Yb(NO3)3(C11N2O2H22)2 crystallizes in the orthorhombic system (P2(1)2(1)2(1) space group; a = 9.3542(1) A, b = 18.1148(2) A, c = 19.7675(2) A; alpha = beta = gamma = 90 degrees; Z = 4). In the solvent phase, the metal polyhedron was found to be similar to that of the solid-state complex Nd(NO3)3(TEMA)2 for M = Nd to Ho. For M = Yb and Lu, a significant elongation of one nitrate oxygen bond was observed. Comparison with measurements on the Am(NO3)3(TEMA)2 complex in ethanol has shown the similarities between the Nd3+ and Am3+ coordination spheres.

Three conformational polymorphs and order-disorder phase transition in a calix

Three polymorphs of a calix[4]arene fixed in the 1,3-alternate conformation by two bridges, a crown-6 on one side and a crown-6 including a photoisomerizable azobenzene unit on the other, 8,11,14,28,31,34,37,40,43,57,60,63-dodecaoxa-2,3-diazanonacyclo[62.2.2.2(4,7).1(16,45).1(26,55).0(15,20).0(22,27).0(44,49).0(51,56)]doheptaconta-1(66),2,4,6,15,17,19,22,24,26,44,46,48,51,53,55,64,67,69-nonadecene, have been characterized by single-crystal X-ray diffraction. In all the polymorphs the azobenzene group is in the more stable trans conformation. The polymorphism arises from the high conformational flexibility of the bridges, which are arranged differently and are highly disordered in the two monoclinic forms (1) and (2a). Form (2a) presents a phase transition near 268 (2) K, leading to a triclinic form (2b), differing from the high-temperature form by some ordering of the chains and a subsequent reduction in crystallographic site multiplicity. The evolution of the cell parameters and peak width with temperature has been investigated down to 173 (2) K. Adiabatic calorimetry measurements indicate a smooth transition centered at 265.0 (1) K, with a heat capacity jump of 60 mJ g(-1) K(-1), suggesting a second-order nature for the transition.