The use of conductivity measurements in organic solvents for the characterisation of coordination compounds

The halogen bond occurs when there is evidence of a net attractive interaction between an electrophilic region associated with a halogen atom in a molecular entity and a nucleophilic region in another, or the same, molecular entity. In this fairly extensive review, after a brief history of the interaction, we will provide the reader with a snapshot of where the research on the halogen bond is now, and, perhaps, where it is going. The specific advantages brought up by a design based on the use of the halogen bond will be demonstrated in quite different fields spanning from material sciences to biomolecular recognition and drug design.

The Halogen Bond

The electronic properties and stereochemistry of mono-nuclear complexes of the copper(II) ion

The purpose of this critical review is to give a representative and comprehensive overview of the arising developments in the field of magnetic metal–organic frameworks, in particular those containing cobalt(II). We examine the diversity of magnetic exchange interactions between nearest-neighbour moment carriers, covering from dimers to oligomers and discuss their implications in infinite chains, layers and networks, having a variety of topologies. We progress to the different forms of short-range magnetic ordering, giving rise to single-molecule-magnets and single-chain-magnets, to long-range ordering of two- and three-dimensional networks (323 references).

Magnetic metal-organic frameworks.

Mixed phosphine 2,2'-bipyridine complexes of ruthenium

Relation between the singlet-triplet splitting and the copper-oxygen-copper bridge angle in hydroxo-bridged copper dimers

: The temperature dependence of the magnetic susceptibility and the electron paramagnetic resonance spectra of the thiazole complexes dichloro- and dibromobis(thiazole)copper(II) are reported, along with a complete three-dimensional X-ray structure analysis of the dichloro complex based on counter data. The dichloro complex, Cu(C3H3NS)2C12, crystallizes in space group of the monoclinic system with two independent formula units in a cell of dimensions a = 7.332(6), b = 3.853(4), c = 17.493(17) angstrom, and Beta = 93.70(1). The structure has been refined by full-matrix least-squares methods using 1172 independent data to a final value of the conventional R-factor (on F) of 0.028. The structure, which consists of infinite chains of doubly chloride bridged copper(II) ions, is reminiscent of those of the pyridine analogs, with a Cu-Cu separation of 3.853(4) angstrom and bridging angle of 91.89(2). The magnetic data and interchain exchange interactions are discussed in the light of the structural properties of the systems.

Magnetic and structural characterization of dibromo- and dichlorobis(thiazole)copper(II)

: Magnetic susceptibility data have been collected for catena-octanedionebis-(thiosemicarbazonato)copper(II), Cu-OTS, and catena-hexane-dionebis(thiosemicarbazonato(copper(II), Cu-HTS, in the temperature range 1.8-120 K, and the data analyzed in terms of an alternating chain Heisenberg exchange model to yield J = -10.1 + or - 0.2/cm, alpha = 0.91 + 0r - 0.02, and g = 2.06 + or - 0.02 for Cu-HTS and J = 12.9 + or - 0.2 alpha = 0.90 + or - 0.02, and g = 2.11 + or - 0.02 for Cu-OTS. Anomalies in the temperature dependent capacitance data for catena-di-micron-chlorobis(4-methylpyridine)copper(II) and catena-di-micron-bromo(N-methylimidazole)copper(II) provide evidence for structural phase transitions presumably from uniform chain structures at room temperature to alternating chain structures at low temperatures. Magnetic parameters for Cu(4-methylpyridine)2Cl2 are J = -9.6 + or - 0.2/cm, g = 2.17 + or - 0.02 and alpha = 0.67 + or - 0.02. An expression for the magnetic susceptibility of a Heisenberg alternating chains of S = 1/2 ions has been developed in terms of the alternation parameter, the exchange coupling constant, and the g factor. (Author)

https://apps.dtic.mil/sti/pdfs/ADA093587.pdf

Exchange Coupling in the Alternating Chain Compounds Catena-Di-micron-chlorobis(4-Methylpyridine)Copper(II), Catena-Di-micron-bromobis-(N-Methylimidazole)Copper(II), Catena-hexanedionebis(Thiosemicarbazato)Copper(II), and Catena-octanedionebis(thiosemicarbazato)Copper(II).

Electronic Structure and Redox Properties of the Clusters [Ru3O(CH3CO2)6L3]n+

: The crystal and molecular structure of the compound catena-micron-oxo-hemiporphyrazinatoiron(IV), (Fe0N8C26H14n), has been determined from single-crystal, three-dimensional X-ray diffraction counter data. The compound crystalizes as blue-black needles in space group P2/n with Z = 2 and having unit cell dimensions (at 210 K) a = 16.090 (3) angstroms, b = 3.975 (2) angstroms, c = 16.070 (3) and beta = 92.97 (1). The structure was refined by full-matrix least-squares techniques to a conventional R value of 0.054. Distorted hemiporphyrazinatoiron units stack along the b axis and are linked into polymeric, uniformly spaced, linear chains by axially-bound oxygen bridges. The oxygen atoms are disordered into two crystallographically distinct sites lying about a central location which is normal to the C2 axis collinear with the chain. The Fe-0-Fe angles are 158.2 and 170.5, and the Fe-0 bond distances range from 1.973 angstroms to 2.030 angstroms, Mossbauer spectral studies at 4.2 K, room temperature and at 420 K reveal that there are two iron sites in the chain as a result of the disorder of the oxygen atoms, and the spectrum is essentially temperature independent. Magnetic susceptibility studies reveal that the iron ions are antiferromagnetically coupled in an alternating chain with J = -133 per cm, g = 2.3 and an alternation parameter of 0.4.

William E. Hatfield

Papers

Relation between the singlet-triplet splitting and the copper-oxygen-copper bridge angle in hydroxo-bridged copper dimers

Magnetic and structural characterization of dibromo- and dichlorobis(thiazole)copper(II)

Exchange Coupling in the Alternating Chain Compounds Catena-Di-micron-chlorobis(4-Methylpyridine)Copper(II), Catena-Di-micron-bromobis-(N-Methylimidazole)Copper(II), Catena-hexanedionebis(Thiosemicarbazato)Copper(II), and Catena-octanedionebis(thiosemicarbazato)Copper(II).

Electronic Structure and Redox Properties of the Clusters [Ru3O(CH3CO2)6L3]n+

Synthesis, Structure and Magnetic Properties of Catena-Micron-Oxo-Hemiporphyrazinatoiron(IV), the First Polymeric Micron-Oxo-Bridged Complex of Iron.