Mononuclear and polynuclear 5-coordinate zinc(II) model complexes: a quantum chemical calibration study of their structure and energy

Zinc-seamed pyrogallol[4]arene dimers as structural components in a two-dimensional MOF

“…In earlier quantum chemical calibration studies, we examined zinc complexes composed of combinations of hydroxide, water and solvent ligands (e.g., Zn(OH) 2 (H 2 O) 2 L 1,2 ) or deprotonated (Z)-ethene-1,2-diol and solvent molecules (Zn(C 2 O 2 H 3 ) 2 L) as possible mononuclear zinc models for the metal centres in PgC x Zn dimers such as 1. 22,23 The solvent ligands L included C 5 H 5 N, NH 3 , CH 3 OH, (CH 3 ) 2 NCHO and (CH 3 ) 2 SO. Although optimization of the hydroxide-containing models yielded mainly 4-coordinate zinc complexes with outer-shell hydrogenbonded networks, optimization of the Zn(C 2 O 2 H 3 ) 2 L complexes yielded 5-coordinate zinc complexes with average Zn-X bond lengths and X-Zn-Y bond angles within the ranges observed experimentally for the zinc-seamed PgC nanocapsules.…”

“…To improve the energetics, single-point energies were evaluated at the MP2/B2-PP//M05-2X/B2-PP level of theory. 22,23 All calculations were performed with use of the Gaussian 09 package. 26…”

The reactions of α-amino acids and α-amino acid esters with high valent transition metal halides: synthesis of coordination complexes, activation processes and stabilization of α-ammonium acylchloride cations

“…Nb(2)-Cl 72.3555 9Nb(2)-Cl 82.2641 (10) Nb(2)-Cl 92.3318 10Nb(2)-Cl 102.3250 (10) Nb(2)-Cl 112.2918 9Nb 2 (10) 174. 26(3) Cl(9)-Nb(2)-Cl (11) 163 At variance to the other a-amino acid ester complexes of niobium in this work, compound 13 is a neutral species in solution with a single 93 Nb resonance at À493 ppm. DFT calculations suggest a mononuclear structure (Fig.…”

“…In general, 1,2-enediols are quite unstable species, 24 whose stabilization may be supplied by hydrogen-bonded protons, 25 or by chelating (N,O) coordination to transition metals. 26 Basically, the process leading to 3 is a C-C bond forming condensation of two proline units (Scheme 5A). Differently, typical a-amino acid condensation generates a peptide bond (Scheme 5B).…”

Interplay of thermochemistry and structural chemistry, the journal (volume 24, 2013, issues 5–6) and the discipline

“…Mayhan et al [195] used DFT to investigate the geometric parameters, including zinc bond lengths and bond angles, of mononuclear zinc complexes [Zn(C 2 O 2 H 3 ) 2 Y (C 2 O 2 H 3 = (Z)-ethene-1,2-diol-1-ate and Y = NH 3 , C 5 H 5 N, CH 3 OH, (CH 3 ) 2 NCHO, (CH 3 ) 2 SO))] as well as the energetics of the complexes, including bond dissociation enthalpies of the Y ligands. In the absence of any chelating metal ion, what is the enthalpy of formation difference of the ligands (Z)-and (E)-ethene-1,2-diol-1-ate?…”