82 Current Inorganic Chemistry, 2015, Vol. 5, No. 2
Editorial
Editorial Recent Advances in Chemistry and Applications of Oximes and their Metal Complexes: Part II Oximes represent organic molecules containing the >C=N-OH fragment, which have been widely used as excellent ambidentate and ampolydentate ligands in analytical, inorganic and bioinorganic chemistry. There is a variety of oximes: aliphatic monoximes derived from aldehydes or ketones, alpha-dioximes, and recently new subclasses of amino/imido oximes and cyanoximes have emerged and received considerable attention. The oximes readily form stable Werner-type complexes with the majority of the metals in the Periodic Table. The compounds often have unusual crystal structures, form coordination polymers and homo- or hetero-metallic polynuclear compounds which demonstrate interesting magnetic properties. Certainly, many metallo-oximates possess biological activity such as cytotoxicity, antimicrobial, or act as structural or functional models of enzymes and cofactors such as cobalamine, for example. This issue of Current Inorganic Chemistry is the first of its kind and dedicated exclusively to synthetic aspects, investigation of thermodynamic properties, structural chemistry and spectroscopic properties of a large variety of oximes and their metal complexes. Here, an interested reader can find selected topics describing recent advances of chemistry of oximes and their metal complexes including aspects of their potential applications. There are two parts of “Recent advances in chemistry of oximes and their metal complexes” which contain 9 contributions received from 3 continents and with authors/co-authors from 11 countries. Part II of this special issue consists of four contributions as original papers. A rather unique paper by Prof. Igor Nikolaenko (Pietermaritzburg, South Africa) thoroughly describes thermodynamic properties of a new bis-oxime ligand. Step-wise protonation constants were determined and revealed remarkable spectroscopic and structural/conformational changes in the new ligand upon variations in pH of aqueous solutions. A large paper by Dr. Daniela Marcano (Texas, USA) is dedicated to comprehensive studies of both solutions and solid state properties of a new 2-pyridylcyanoxime ligand. Thus, its protonation constants and pronounced solvatochromism of derived anion were measured and investigated for the first time. A series of ionic EPh4+ salts (E=P, As) and transition metals complexes of Ni, Fe with 2-pyridylcyanoxime was prepared and characterized using a variety of spectroscopic methods, including 57Fe Mössbauer spectroscopy, and X-ray analysis. An interesting paper by Prof. Igor Fritsky (Kiev, Ukraine) describes the synthesis, spectroscopic properties and crystal structures of Nickel(II) and Iron(II) complexes with the oxime-containing cores that were used as mononuclear building blocks for supramolecular assemblies. Finally, a fascinating large paper by Dr. Sergiy Tyukhtenko (Massachusetts, USA) provides insights into the structures of a classic organic reagents used for analysis of a variety of transition metals – isomeric “1,2- and 2,1-nitroso-naphthols”. Despite many years of use of these powerful chelating ligands their solid state and solutions structures were not reliably established. Thus lead to numerous and persistent speculations about the existence of the nitroso-oxime tautomerism for both ligands. It was found that both compounds are oximes in solid state. A detailed spectroscopic studies including 1H, 13C and 15N NMR spectroscopy provided undisputed evidence of the existence of both isomeric compounds in solutions as oximes as well. In both cases there is a strong intramolecular H-bonding in the oxime-ketone “closed” structures manifested as the formation of sixmembered cycles in low polarity solvents, and the formation of an “open” intermolecular H-bonded oxime-ketone structures in polar donor solvents. I hope that the reader of this special issue of Current Inorganic Chemistry will enjoy this short excursion into wonderful world of oximes and their numerous metal complexes.
Nikolay Gerasimchuk (Guest Editor) Department of Chemistry, Temple Hall 456, Missouri State University 901 South National Avenue, Springfield, MO 65897 USA Tel: 1-417-836-5165 Fax: 1-417-836-5507 E-mail:
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