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Relevant academic research and scientific papers

Synthesis, structural, and insulin-enhancing studies of oxovanadium(iv) complexes

Oxovanadium(iv) complexes with Schiff bases derived from substituted salicylaldehyde and diamine have been prepared and characterized. 1H NMR and IR spectral data revealed that the symmetrical Schiff base was isolated, and elemental analysis confirmed the

Influences of polarizability effect of alkyl group and homoring competition effect of substituents on the NMR spectra of salen-type Schiff base

Salen-type Schiff bases are a kind of important compounds and are widely used. In order to explore the effect of alkyl groups and substituents attached to aromatic ring on the chemical shifts, 63 title compounds were synthesized. Their 1H NMR and 13C NMR spectra were obtained; and the effects of the alkyl chain length and substituents on the chemical shifts (δH(CH=N), δC(CH=N), δH(OH), and δC(C-OH)) were studied. The results show that (1) the alkyl polarizability effect index (PEI) has an important influence on the chemical shifts of the above four atoms, with the increase of PEI, the values of δH(CH=N) and δc(CH=N) decrease, and the values of δH(OH) and δC(C-OH) increase. (2) The influence of substituent X attached to aromatic ring on the chemical shift is related to its position by taking OH or CH=N as reference. As for the effect of substituent on the chemical shifts, the effect of Hammett constant σ(X)-OH and excited-state substituent parameter (Formula presented.) with OH as reference are different from that ofσ(X)-CH=N and (Formula presented.) with CH=N as reference, and there is a “homoring competition effect” of the substituent. (3) The effect of the cross-interaction between X and OH on the chemical shift is also significantly different due to the different position of X. Quantitative correlation equations against chemical shifts were built for the four atoms, and the stability and prediction ability of the obtained equations were confirmed by leave-one-out cross validation.

Iridium(I) homobinuclear complexes containing salen-type ligands as bridge

New binuclear iridium(I) complexes with general formula [Ir2(η4-cod)2(μ-SB)] (1–12) derived from the reactions of tetradentate Schiff bases ligands [N,N′-ethylenebis(5-R-salicylideneimine)] (5,5′-R-salenH2), [N,N′-1,3-propylenebis(5-R-salicylideneimine)] (5,5′-R-salpenH2), and [N,N′-o-phenylenebis(5-R-salicylideneimine)] (5,5′-R-salphenH2) (R = H, MeO, Cl, NO2) with [Ir(cod)(μ-Cl)]2 were synthesized. The homobinuclear nature of this iridium complexes was supported by elemental analysis, FAB-Mass and 1H NMR spectrometry. Full characterization was accomplished by IR spectroscopy, 13C NMR and bidimensional NMR experiments (COSY, HSQC, HMBC and NOESY). In addition, iridium complex [(Ir(η4-cod)2(μ-5,5′-MeO-salen)] (2) was characterized by X-ray crystallography, showing that ethylene bridge is a s-trans conformation, and that the Schiff base ligand act as a bridging N,O-bidentate ligand toward two iridium atoms, and 1,5-cyclooctadiene (cod) ligand complete the coordination sphere of metal center. The effect of the substituent groups on salicylaldiminate fragments has been studied by 13C{1H} NMR shift and Hammett sigma correlations for each series of complexes.