Electrical conduction is well understood in materials formed from inorganic or organic building blocks, but their combination to produce conductive hybrid frameworks and networks is an emerging and rapidly developing field of research. Self-assembling organic–inorganic compounds offer immense potential for functionalising material properties for a wide scope of applications including solar cells, light emitters, gas sensors and bipolar transparent conductors. The flexibility of combining two distinct material classes into a single solid-state system provides an almost infinite number of chemical and structural possibilities; however, there is currently no systematic approach established for designing new compositions and configurations with targeted electronic or optical properties. We review the current status in the field, in particular, the range of hybrid systems reported to date and the important role of materials modelling in the field. From theoretical arguments, the Mott insulator-to-metal transition should be possible in semiconducting metal–organic frameworks, but has yet to be observed. The question remains as to whether electro-active hybrid materials will evolve from chemical curiosities towards practical applications in the near term.

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Conductive metal–organic frameworks and networks: fact or fantasy?

Copper thiocyanate compounds with three different oxidation states, Cu(I)(admtrz)SCN (1), [Cu(I)(2)Cu(II)(admtrz)(6)(SCN)(2)](ClO(4))(2) (2), and [Cu(II)(3)(admtrz)(4)(SCN)(3)(mu(3)-OH)(H(2)O)](ClO(4))(2)H(2)O (3), have been synthesized and characterized (admtrz = 4-amino-3,5-dimethyl-1,2,4-triazole) Compounds 1 and 3 crystallize in the space group Pbca of the orthorhombic system with eight formula units in cells of dimensions a = 80221(2) A, b = 323844(1) A, c = 135659(3) A, R1/wR2 = 00595/01674 for compound 1 and a = 21501(3) A, b = 18382(2) A, c = 21526(2) A, R1/wR2 = 00638/01519 for compound 3 Compound 2 crystallizes in the space group C2/c of the monoclinic system with four formula units in cells of dimensions a = 18772(4) A, b = 11739(2) A, c = 22838(5) A, beta = 9111(3) degrees, R1/wR2 = 00482/01265 The layered-type structure of 1 can be regarded as constructed from the tetranuclear copper units double bridged by one of the two unique thiocyanate and admtrz ligands, which are bridged by the other unique thiocyanate ligands to form a two-dimensional layered structure along the a and b directions The linear trinuclear copper cation in mixed-valence compound 2 consists of one two-valence copper and two one-valence copper atoms which are bridged by admtrz ligands, and the external copper(I) atoms are coordinated by terminal thiocyanate The EPR spectra of 2 show the existence of localized mixed-valence copper ions The triangle trinuclear copper cation in compound 3 has its Cu(3) triangle capped by one apical mu(3)-OH group, each edge bridged by a bridging admtrz ligand and each Cu atom coordinated by a N atom from the terminal thiocyanate, while one of the three edges is further bridged by another admtrz ligand and the opposite Cu1 atom is coordinated by a water molecule The EPR and magnetic susceptibility of compound 3 were studied, showing antiferromagnetic behavior

Different oxidation states of copper(I, I/II, II) thiocyanate complexes containing 1,2,4-triazole as a bridging ligand: syntheses, crystal structures, and magnetic properties of 2-D polymer Cu I(admtrz)SCN, linear trinuclear [CuI2CuII(admtrz)6(SCN)2](ClO4)2, and triangular trinuclear [CuII3(admtrz)4(SCN)3(mu3-OH)(H2O)](ClO4)2.H2O (admtrz = 4-amino-3,5-dimethyl-1,2,4-triazole).

Structural isomerism of copper(II) compounds

Mixed-valence Cu(II)/Cu(I) complex of quinolone ciprofloxacin isolated by a hydrothermal reaction in the presence of L-histidine: comparison of biological activities of various copper-ciprofloxacin compounds.

Inorganic chemistry and biology can benefit greatly from each other. Although synthetic and physical inorganic chemistry have been greatly successful in clarifying the role of metal ions in biological systems, the time may now be right to utilize biological systems to advance coordination chemistry. One such example is the use of small, stable, easy-to-make, and well-characterized proteins as ligands to synthesize novel inorganic compounds. This biosynthetic inorganic chemistry is possible thanks to a number of developments in biology. This review summarizes the progress in the synthesis of close models of complex metalloproteins, followed by a description of recent advances in using the approach for making novel compounds that are unprecedented in either inorganic chemistry or biology. The focus is mainly on synthetic "tricks" learned from biology, as well as novel structures and insights obtained. The advantages and disadvantages of this biosynthetic approach are discussed.

Biosynthetic inorganic chemistry.

Mixed-valence copper(I)copper(II) compounds: analysis and classification of crystallographic data

Cu(OPph3)2Cl2 exists in yellow α- and orange β-isomeric forms. β-Cu(OPph3)2Cl2 was prepared by thermal decomposition of Cu(OPph3)4Cl2·2 H2O and by reaction of CuCl2 with OPph3 in acetone—ethanol mixture at higher temperature. The results of magnetic measurements, electronic andESR spectra show that the structure of β-isomer differs from the known structure of the α-isomer by a different degree of distortion of the coordination tetrahedron. α-Cu(OPph3)2Cl2 is thermodynamically more stable then β-Cu(OPph3)2Cl2.

Darstellung und Eigenschaften zweier isomerer Formen des Dichloro-bis[triphenylphosphinoxid—Kupfer(II)]-Komplexes

Magnetic exchange coupling in tetranuclear copper clusters of the type [Cu4(μ4O)Cl6−nBrnL4]

The X-ray crystal structure of Cu(OPPh3)4(H2O)2Cl2 shows that the compound is an adduct of dichlorodiaquacopper(II) and triphenylphosphine oxide; the adduct unit is formed by one CuCl2(H2O)2 square-planar complex unit and four molecules of triphenylphosphine oxide which are bonded to the comlplex unit by hydrogen bonds.

Crystal and molecular structure of the adduct between dichlorodiaqua-copper(II) and triphenylphosphine oxide

By replacement of methanol in the Cu4OX6(MeOH)4 (X Cl, Br) complexes with thiourea (tu), N,N′-diphenylthiourea (diftu), N,N′-dimethlthiourea (dimtu), tetramethylthiourea (tmtu) and acetylthiourea (actu), the complexes Cu4OCl6L4 where L tu, tu(0.3 Et2O), diftu, dimtu, tmtu, actu (0.5Et2O) and the complexes Cu4OBr6L4, where L tu, diftu, dimtu, tmtu have been prepared. Their infrared and electronic spectra indicate the presence of Cu4O grouping and the trigonal bipyramidal coordination of copper(II). These complexes exhibit e.p.r. signals in the temperature range 100–260 K, in contrast to other known complexes of this structural type, which showed the e.p.r. signals at significantly lower temperatures. Thiourea and its derivatives are not able to reduce copper(II) in reaction with the tetranuclear Cu4OX6(MeOH)4 complexes in methanol-ether solution due to the redox stabilizing effect of the tetranuclear structure.

Gregor Ondrejovič

Papers

Mixed-valence copper(I)copper(II) compounds: analysis and classification of crystallographic data

Darstellung und Eigenschaften zweier isomerer Formen des Dichloro-bis[triphenylphosphinoxid—Kupfer(II)]-Komplexes

Magnetic exchange coupling in tetranuclear copper clusters of the type [Cu4(μ4O)Cl6−nBrnL4]

Crystal and molecular structure of the adduct between dichlorodiaqua-copper(II) and triphenylphosphine oxide

Tetranuclear Thioureacopper(II) Complexes