The reaction of the tripodal tetradentate dibasic ligand 6,6'-(2-(pyridin-2-yl)ethylazanediyl)bis(methylene)bis(2,4-di-tert-butylphenol), H2L(1)I, with [V(IV)O(acac)2] in CH3CN gives the V(V)O-complex, [V(V)O(acac)(L(1))] 1. Crystallisation of 1 in CH3CN at ∼0 °C gives dark blue crystals of 1, while at room temperature it affords dark green crystals of [{V(V)O(L(1))}2μ-O] 3. Upon prolonged treatment of 1 in MeOH, [V(V)O(OMe)(MeOH)(L(1))] 2 is obtained. All three complexes were analysed by single-crystal X-ray diffraction, depicting a distorted octahedral geometry around vanadium. In the reaction of H2L(1) with V(IV)OSO4 partial hydrolysis of the tripodal ligand results in the elimination of the pyridyl fragment of L(1) and the formation of H[V(V)O2(L(2))] 4 containing the ONO tridentate ligand 6,6'-azanediylbis(methylene)bis(2,4-di-tert-butylphenol), H2L(2)II. Compound 4, which was not fully characterised, undergoes dimerization in acetone yielding the hydroxido-bridged [{V(V)O(L(2))}2μ-(OH)2] 5 having a distorted octahedral geometry around each vanadium. In contrast, from a solution of 4 in acetonitrile, the dinuclear compound [{V(V)O(L(2))}2μ-O] 6 is obtained, with a trigonal bipyramidal geometry around each vanadium. The methoxido complex 2 is successfully employed as a functional catechol-oxidase mimic in the oxidation of catechol to o-quinone under air. The process was confirmed to follow a Michaelis-Menten type kinetics with respect to catechol, the Vmax and KM values obtained being 7.66 × 10(-6) M min(-1) and 0.0557 M, respectively, and the turnover frequency is 0.0541 min(-1). A similar reaction with the bulkier 3,5-di-tert-butylcatechol proceeded at a much slower rate. Complex 2 was also used as a catalyst precursor for the oxidative bromination of thymol in aqueous medium. The selectivity shows quite interesting trends, namely when not using excess of the primary oxidizing agent, H2O2, the para mono-brominated product corresponds to ∼93% of the products and no dibromo derivative is formed.

Photodynamic therapy is a promising cancer treatment that induces apoptosis as a result of the interactions between light and a photosensitizing drug. Lately, the emergence of biocompatible nanoparticles has revolutionized the prospects of photodynamic therapy (PDT) in clinical trials. Consequently, a lot of research is now being focused on developing non-toxic, biocompatible nanoparticle-based photosensitizers for effective cancer treatments using PDT. In this regard, semiconducting quantum dots have shown encouraging results. Quantum dots are artificial semiconducting nanocrystals with distinct chemical and physical properties. Their optical properties can be fine-tuned by varying their size, which usually ranges from 1 to 10 nm. They present many advantages over conventional photosensitizers, mainly their emission properties can be manipulated within the near IR region as opposed to the visible region by the former. Consequently, low intensity light can be used to penetrate deeper tissues owing to low scattering in the near IR region. Recently, successful reports on imaging and PDT of cancer using carbon (carbon, graphene based) and metallic (Cd based) based quantum dots are promising. This review aims to summarize the development and the status quo of quantum dots for cancer treatment.

Octamethoxy vanadylporphyrin (1) and its perbromo derivative (2) have been synthesized. 2 exhibited 100% selectivity for epoxide formation with very high TOF numbers. Remarkably, 2 biomimics vanadium bromoperoxidase (VBrPO) enzyme with extremely high TOF value in water.

The reactions of the tripodal tetradentate ONNO donor ligands 6,6′‐{[(2‐morpholinoethyl)azanediyl]bis(methylene)}bis(2,4‐di‐tert‐butylphenol) (H2L1), 6,6′‐{[(2‐morpholinoethyl)azanediyl]bis(methylene)}bis(2,4‐dimethylphenol) (H2L2) and 6,6′‐{[(2‐morpholinoethyl)azanediyl]bis(methylene)}bis[2‐(tert‐butyl)‐4‐methylphenol] (H2L3) with [MoVIO2(acac)2] (acac = acetylacetonato) in a 1:1 molar ratio in MeOH gave the corresponding cis‐dioxidomolybdenum(VI) complexes [MoO2(L1)], [MoO2(L2)] and [MoO2(L3)], respectively, in excellent yields. These complexes were characterized by various spectroscopic (IR, UV/Vis, 1H and 13C NMR), electrochemical, thermogravimetric, single‐crystal XRD, and powder XRD (PXRD) studies. In these complexes, the geometry around the cis‐[MoO2]2+ core is distorted octahedral, and the ligands are tetradentate and coordinate through two Ophenolate, one Ntripodal, and one Nmorpholine atoms. One of the oxido groups and the morpholine nitrogen atom occupy the axial sites. These complexes were used for catalytic oxygen atom transfer between benzoin and dimethyl sulfoxide (DMSO) in acetonitrile at 80 °C, and the formation of benzil was followed by HPLC. Detailed kinetic studies revealed a first‐order rate in benzoin and catalyst, and the rate constant for the second‐order oxygen atom transfer reaction was 0.0162 m–1 h–1. The formation of the dinuclear intermediates [LMoV–µ‐O‐MoVL] was established by MALDI‐TOF MS and UV/Vis spectroscopy. Its reversible nature was further supplemented by UV/Vis spectroscopy. These complexes also catalyze the oxidation of pyrogallol in a fashion similar to that of transhydroxylases. Under aerobic conditions, the initially formed oxidation product phloroglucinol undergoes further oxidative coupling in the presence of H2O2 to give purpurogallin as the final product. This process follows Michaelis–Menten‐type kinetics with respect to pyrogallol; the kcat values obtained were 394, 300 and 247 h–1 for [MoVIO2(L1)], [MoVIO2(L2)] and [MoVIO2(L3)], respectively.

Dioxidomolybdenum(vi) complexes of tetradentate ONNO donor Mannich base ligands for the catalytic oxygen atom transfer between benzoin and DMSO are reported.