Herein, biologically crucial amino acids have been explored for the synthesis of fluorescent organotin compounds. One-pot reaction of dimethyltin oxide, 2-hydroxy-4-methoxybenzophenone and α-amino acids, i.e., glycine, L-isoleucine and L-methionine, afforded respective organotin compounds with biogenic Schiff base skeletons 1–3. Although all the compounds were constituted from similar ONO type Schiff base units, only compound 1 (derived from glycine) crystallized as a hexacoordinated organotin compound of the type (ONO)SnMe2(MeOH) with a tridentate chelating Schiff base ligand. Analogous syntheses with L-isoleucine and L-methionine did not afford the related Schiff base compounds 2 and 3. Instead, some kind of precursors, namely 2′ and 3′, crystallized as solvent mediated Sn4O4 ladders and two Schiff base ligand moieties bound to the terminal Sn atoms via carboxylate moiety only. Interestingly, solution NMR spectroscopy (1H, 13C, 119Sn) of 1 unambiguously complied with its solid state structure while for 2′ and 3′ the behaviour was entirely different suggesting their transformation to mononuclear compounds 2 and 3 in solution phase. The distinctive structural aspects of 2′/2 and 3′/3 in solid and solution phase were also supported by solid state 119Sn CP/MAS NMR studies. All the compounds were found to be fluorescent when excited at 365 nm and the solutions of compound 3′ experienced quenching in the presence of paramagnetic metal ions due to chelation enhanced quenching.

Fluorescent biogenic Schiff base compounds of dimethyltin

Stability, lability, spectral parameters and structure of complexes and stereoselective effects in the nickel(II) – l/d/dl-histidine – l/d/dl-methionine systems

Here we report the studies on selenium coordination compounds, in particular selenium nanoparticles (Nps), that can be used in pharmacology. The Se Nps were synthesized by three pathways and characterized by FT-IR, XRD, SEM, TEM, and EDX analyses. Сomplexes of Se(0) with alanine, tyrosine, serine, aspartic acid, histidine, and glycine as ligands, are synthesized in a 1: 2 molar ratio. IR spectra of solid complexes indicate that selenium metal is coordinated with the amino and carboxylate groups. The complexes are square planar structures with two amino acids bidentate ligands occupying the corners. Binary complexes of Se Nps with Ala, Tyr, Ser, Asp, His, and Gly react readily with vitamine B3 (nia) affording mixed ligand complexes of the types [Se(AA)2(nia)2], where AA indicates the above aminoacids. These complexes are determined to have a 1 : 2 : 2 (Se : AA : nia) stoichiometry with coordination number 6. The structures of products are studied by FT-IR, Raman and UV-Vis spectra, XRD, SEM/TEM, and TG/DTG. Conductance of the complexes in DMSO indicates their non-electrolytic nature. The complexes demonstrate antioxidant activity with potent scavenging property.

Synthesis and Characterization of New Nano-Sized Selenium Compounds to Further Use as Antioxidants Drugs

In the present work the chemical speciation of ternary complexes systems formed by VO2+ ion with picolinic acid and the amino acids = α-alanine (HαAla), glycine (HGly), serine (HSer), threonine (HT...

Speciation studies of binary and ternary complexes formed with oxidovanadium(IV) ion picolinic acid and some amino acids

In this work, the ligand 2-methylquinoline-8-carboxylic acid (HL) was prepared using a modification of a previous protocol, and its protonation constants were studied. The stability constants of th...

Kenneth Puche

Papers

Stability of nickel(II) binary and ternary complexes with dipicolinic acid and the amino acids serine, threonine, methionine and phenylalanine