Synthesis, structure, solution chemistry and the electronic effect of para substituents on the vanadium center in a family of mixed-ligand [VVO(ONO)(ON)] complexes

Oxidovanadium complexes with tridentate aroylhydrazone as catalyst precursors for solvent-free microwave-assisted oxidation of alcohols

“…Two of the complexes (1 and 2) were already known and were synthesized by a reported method [50][51][52][53][54][55][56][57][58][59][60][61][62], whereas the other two (3 and 4) were newly synthesized and are now reported (Scheme 1).…”

“…Sometimes, the presence of a neutral bidentate N,N donor auxiliary ligand in CH 3 CN helps to stabilize the oxidovanadium(IV) centre, which can be isolated as a stable solid product [59,60]. Herein, we used two different bidentate auxiliary ligands to stabilize oxidovanadium centres in 3 and 4: the mono negative 8-hydroxyquinolinate (hq − ) and the neutral 1,10-phenanthroline (phen) which stabilize the vanadium(V) and the vanadium(IV) centre, respectively, with the tridentate hydrazone Schiff base [48,59,60]. The four complexes of this study (1-4) present different coordination environments and have been used for a comparative study of their catalytic activities towards solventfree MW-assisted oxidation of secondary alcohols.…”

“…The electronic spectrum of the oxidovanadium(V) complex 3 in acetonitrile solution displays a strong absorption at 552 nm assigned to the PhO − → V(d ) LMCT transition and three other intense absorption band in the 331-240 nm region allocated to intraligand ( → *) transitions [59]. The oxidovanadium(IV) complex 4 exhibits a low intensity band at 701 nm due to ligand field d xz , d yz → d xy transitions of the VO 2+ centre [60].…”

“…1). The vanadium ion exhibits a distorted octahedral O 4 N 2 coordination (quadratic elongation of 1.048 and angle variance of 104.79 [48,59], the four vanadium oxygen bond lengths in 3 follow the order: oxido < phenolate < enolate. Fig.…”

Variation in the biomolecular interactions of nickel(ii) hydrazone complexes upon tuning the hydrazide fragment

“…41 Further, the bands appeared around 370 and 450 nm for complexes have been assigned to ligand-to-metal charge transfer (LMCT) as well as metal-to-ligand charge transfer (MLCT) transitions, respectively. 42,43 The electronic absorption spectra of compounds (ligands/complexes) 1-6 without as well as with the added CT DNA is shown in Fig. S3, S4 † and 3.…”