Iron(III) spin crossover compounds

In this chapter, selected results obtained so far on Fe(III) spin crossover compounds are summarized and discussed. Fe(III) spin transition materials of ligands containing chalcogen donor atoms are considered with emphasis on those of N,N-disubstituted-dithiocarbamates, N,N-disubstituted-XY-carbamates (XY=SO, SSe, SeSe), X-xanthates (X=O, S), monothio-β-diketonates and X-semicarbazones (X=S, Se). In addition, attention is directed to Fe(III) spin crossover systems of multidentate Schiff base-type ligands. Examples of spin inter-conversion in Fe(III) compounds induced by light irradiation are given.

Corporate governance disclosure in the Gulf countries

Corporate governance disclosure is important for countries aiming to attract international investors and reduce companies’ cost of capital. The relationship between corporate governance disclosure (CGD) and its determinants is the main objective of the current research. Accordingly, the research aimed to: (i) assess CGD level in the Gulf countries; (ii) investigate the impact of ownership structure (proportion of institutional, governmental, managerial and family ownership) on CGD; (iii) explore the effect of board characteristics (proportion of independent board members, proportion of family members on board, CEO/chairman duality and board size) on CGD; (iv) examine the relationship between diversity (proportion of foreign and female members on a board and in the senior management team) and CGD; and (v) test the association between firm characteristics (company size, age, liquidity, profitability, leverage, industry and auditor types) and CGD. Gulf countries (Bahrain, Kuwait, Oman, Qatar, Saudi Arabia, and the United Arab Emirates) were selected for the study since they share similar characteristics and represent a relatively homogeneous category in the Middle East and North African region. A CGD index of 232 items was developed and divided into six categories: ownership structure and investor rights; financial transparency and information disclosure; information on auditors; board and senior management structure and process; board committees; and finally corporate behaviour and responsibility. Annual reports available for listed non-financial companies of the Gulf countries were 270 for the year 2009. The maximum CGD level was 63%, whereas the minimum was 5%, with an average disclosure level of 32%. Several regression models were conducted to enhance the robustness of the results and conclusions of the study. The results indicated that five variables had a significant positive relationship with CGD: proportion of independent members on a board, proportion of foreign members on a board, proportion of foreign members in the senior management team, auditor type and profitability. The research contributes to the literature on corporate governance voluntary disclosure in developing countries. Practical contributions consist of several recommendations to policy makers, regulators, and professional institutions in the Gulf countries.

Studies on the relative stabilities of Mn(II) and Mn(III) in complexes with N4O2 donor environments:crystal structures of [Mn(pybzhz)2] and [Mn(Ophsal)(imzH)2] ClO4 (pybzhz = N-(benzoyl)-N-(picolinylidene) hydrazine, Ophsal = N,N-o-phenylenebis(salicylideneimine), imzH = imidazole)

Five manganese complexes in an N 4O 2 donor environment have been prepared. Four of the compounds involve aroyl hydrazone as ligands and manganese is in a +2 oxidation state. The fifth compound was prepared using N,Nprime-o-phenylenebis(salicylideneimine) and imidazole as ligands where manganese is present in +3 oxidation state. X-ray crystal structure of one Mn +2 compound and the Mn +3 compound was determined. The relative stabilities of the Mn +2 and Mn +3 oxidation states were analyzed using the structural data and MO calculations. Manganese(II) complexes of four aroyl hydrazone ligands were prepared and characterized by different physicochemical techniques. The complexes are of the type Mn(L) 2, where L stands for the deprotonated hydrazone ligand. One of the compounds, Mn(pybzhz) 2, was also characterized by single crystal structure determination. In all these complexes, the Mn(II) is in an N 4O 2 donor environment and the Mn(II) center cannot be oxidized either chemically or electrochemically. However, when another ligand Ophsal is used to give the compound [Mn(Ophsal)(imzH) 2]ClO 4, which was also characterized by X-ray crystal structure determination, manganese can easily avail the +3 oxidation state. The relative stabilities of the +2 and +3 oxidation states of manganese were analyzed and it was concluded that the extent of distortion from the perfect octahedral geometry is the main controlling factor in these cases. © 2004 Elsevier B.V. All rights reserved.