Determination of enantiomeric excess of leucine and valine by X-ray powder diffraction

Two amino acids, leucine and valine, were studied by X-ray powder diffraction (XRPD). The linear correlations between intensity of racemate (decrease) or enantiomer (increase) and enantiomeric excesses were observed in each case

Unique mononuclear Mn-II complexes of an end-off compartmental Schiff base ligand: experimental and theoretical studies on their bio-relevant catalytic promiscuity

Three new mononuclear manganese(II) complexes, namely [Mn(HL)(2)]center dot 2ClO(4) (1), [Mn(HL)(N(CN)(2)) (H2O)(2)]center dot ClO4 (2) and [Mn(HL)(SCN)(2)] (3) [LH = 4-tert-butyl-2,6-bis-[(2-pyridin-2-yl-ethylimino)-methyl]-phenol], have been synthesized and structurally characterized. An "end-off" compartmental ligand (LH) possesses two symmetrical compartments with N2O binding sites but accommodates only one manganese atom instead of two due to the protonation of the imine nitrogen of one compartment. Although all three complexes are mononuclear, complex 1 is unique as it has a 1 : 2 metal to ligand stoichiometry. The catalytic promiscuity of complexes 1-3 in terms of two different bio-relevant catalytic activities namely catecholase and phenoxazinone synthase has been thoroughly investigated. EPR and cyclic voltametric studies reveal that radical formation rather than metal centered redox participation is responsible for their catecholase-like and phenoxazinone synthase-like catalytic activity. A computational approach suggests that imine bond bound radical generation rather than phenoxo radical formation is most likely responsible for the oxidizing properties of the complexes.Supplementary material: [http://cherry.chem.bg.ac.rs/handle/123456789/3657

Supplementary data for the article: Adhikary, J.; Chakraborty, A.; Dasgupta, S.; Chattopadhyay, S. K.; Kruszynski, R.; Trzesowska-Kruszynska, A.; Stepanović, S.; Gruden-Pavlović, M.; Swart, M.; Das, D. Unique Mononuclear Mn II Complexes of an End-off Compartmental Schiff Base Ligand: Experimental and Theoretical Studies on Their Bio-Relevant Catalytic Promiscuity. Dalton Transactions 2016, 45 (31), 12409–12422. https://doi.org/10.1039/c6dt00625f

Supplementary material: [https://doi.org/10.1039/c6dt00625f]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/2294

The structure of coordination precursors as an effective tool for governing of size and morphology of ZnS and ZnO nanoparticles

The zinc sulphide and zinc oxide micro- and nanoparticles of different shapes were synthesized from the five zinc coordination precursors, via controlled thermal decomposition process. The precursors were synthesized from zinc thiocyanate and N-donor ligands (2-aminopyrimidine, 1H-1,2,4-triazole and hexamethylenetetraamine), and they possessed different molecular and crystal structures (confirmed by X-ray crystallographic and spectroscopic studies). The proper set of parameters of precursors conversion process allows producing of ZnS in cubic (sphalerite) and hexagonal (wurtzite) form, as well as ZnO in hexagonal form. The relationship between the particles geometry (size and morphology) and the precursor structure, as well as the parameters of thermal conversion process was investigated. Keywords: Zinc thiocyanate, Coordination compound, Zinc sulphide, Zinc oxide, Crystal structure, Single precursor metho

Revealing the structural chemistry of the group 12 halide coordination compounds with 2,2′-bipyridine and 1,10-phenanthroline

<p>The coordination compounds of group 12 halides with 2,2′-bipyridine (bpy) and 1,10-phenanthroline (phen), 2[CdF₂(bpy)₂]·7H₂O (<b>1</b>), [ZnI(bpy)₂]⁺·I₃⁻ (<b>2</b>), [CdI₂(bpy)₂] (<b>3</b>), [Cd(SiF₆)H₂O(phen)₂]·[Cd(H₂O)₂(phen)₂]²⁺·F^–·0.5(SiF₆)^2–·9H₂O (<b>4</b>), [Hg(phen)₃]²⁺·(SiF₆)^2–·5H₂O (<b>5</b>), [ZnBr₂(phen)₂] (<b>6</b>), 6[Zn(phen)₃]²⁺·12Br^–·26H₂O (<b>7</b>) and [ZnI(phen)₂]⁺·I^– (<b>8</b>), have been synthesized and characterized by X-ray crystallography, IR spectroscopy, elemental and thermal analysis. Structural investigations revealed that metal : ligand stoichiometry in the inner coordination sphere is 1 : 2 or 1 : 3. A diversity of intra- and intermolecular interactions exists in structures of <b>1</b>–<b>8</b>, including the rare halogen⋯halogen and halogen⋯<i>π</i> interactions. The thermal and spectroscopic properties were correlated with the molecular structures of <b>1</b>–<b>8</b>. Structural review of all currently known coordination compounds of group 12 halides with bpy and phen is presented.</p

Can Stacking Interactions Exist Beyond the Commonly Accepted Limits?

Systematic study of π···π interactions of structurally characterized compounds containing parallel benzene and/or pyridine rings was carried out. The gathered geometrical parameters were analyzed in statistical terms. The quantum mechanical calculations were made for the above-mentioned ring systems in different arrangements and the calculated interaction energy values were referred to the statistical data. The maximum bonding energy of the studied systems is about 3 kcal/mol. The ring rotation about the vertical axis has almost no influence on the system binding energy. In the specific ring arrangements, the stacking interactions can be bonding even for ring centroid distances larger than 6 Å. The results prove that the application of the generally accepted geometrical criteria of stacking interactions leads to the omission of the multiple bonding intermolecular interactions during the interpretation of the reactivity, self-assembly, as well as the properties of the supramolecular compounds

Structural Insights into Influence of Isomerism on Properties of Open Shell Cobalt Coordination System

The two coordination compounds of cobalt were designed and synthesized. The substrates were carefully selected to allow gentle tuning of the molecular structure of the designed compounds. The crystal, molecular and supramolecular structure of studied compounds has been determined and discussed. The spectroscopic and thermal properties of designed coordination compounds have been studied and their application as precursors for the synthesis of cobalt oxide nanoparticles has been demonstrated. It was proven that not only are parameters of conversion of the precursor to nanoparticles important, but also small changes in molecular structure can considerably affect the size of formed particles. For unambiguous determination of the influence of compounds structure on their UV-Vis radiation absorption, density functional theory and time-dependent density functions theory calculations have been performed. The complexity of the correct ab-initio reflection of the open shell molecular system was outlined and discussed. The results obtained from density functional theory (DFT) calculations have been also employed for discussion of the bonding properties