Facile Synthesis of ß-Tetracyano Vanadyl Porphyrin from Its Tetrabromo Analogue and Its Excellent Catalytic Activity for Bromination and Epoxidation Reactions.

Complex 2,3,12,13-tetracyano-5,10,15,20-tetraphenylporphyrinatooxidovanadium(IV) {[VIVOTPP(CN)4], 2} has been prepared by nucleophilic substitution of ß-bromo groups of the corresponding 2,3,12,13-tetrabromo-5,10,15,20-tetraphenylporphyrinatooxidovanadium(IV) {[VIVOTPP(Br)4], 1} using CuCN in quinoline. Both complexes show biomimetic catalytic activity similar to enzyme haloperoxidases and efficiently brominate various phenol derivatives in the presence of KBr, H2O2, and HClO4 in the aqueous medium. Between these two complexes, 2 exhibits excellent catalytic activity with high turnover frequency (35.5-43.3 s-1) due to the strong electron-withdrawing nature of the cyano groups attached at ß-positions and its moderate nonplanar structure as compared to 1 (TOF = 22.1-27.4 s-1). Notably, this is the highest turnover frequency value observed for any porphyrin system. The selective epoxidation of various terminal alkenes using complex 2 has also been carried out, and the results are good, specifying the importance of electron-withdrawing cyano groups. Catalysts 1 and 2 are recyclable, and the catalytic activity proceeds through the corresponding [VVO(OH)TPP(Br)4] and [VVO(OH)TPP(CN)4] intermediates, respectively.

Fused Nickel(II) Porphyrins-Sensing of Toxic Anions and Selected Metal Ions Through Supramolecular Interactions.

Ni(II) porphyrins having fused -NH group were synthesized and characterized by various spectroscopic techniques. The fused porphyrins 1 and 2 were used to detect species of opposite polarity. 1 was used to sense toxic anions viz. cyanide and fluoride ions whereas 2 was used for detecting some selective metal ions including toxic mercury(II) ions. 1 is having acidic -NH proton, which detects anions via hydrogen bonding interactions followed by anion-induced deprotonation. On the other hand, 2 senses the metal species via weak charge transfer interactions from oxygen atom of the formyl group to the added metal ions. The limit of detection was calculated in case of 1 as 2.13 and 3.15 ppm for cyanide and fluoride ions, respectively. Similarly, the detection limit was found to be 0.930, 2.231, and 0.718 ppm for Cu(II), Fe(III), and Hg(II) ions, respectively, for probe 2. The probes were recovered and reused for several cycles.

Vanadyl ß-tetrabromoporphyrin: synthesis, crystal structure and its use as an efficient and selective catalyst for olefin epoxidation in aqueous medium.

We hereby report the synthesis, characterization and catalytic applications in the epoxidation of alkenes by a vanadyl porphyrin having bulky bromo substituents at the ß-positions viz. vanandyltetrabromotetraphenylporphyrin (1). The synthesized porphyrin was characterized by various spectroscopic techniques like UV-visible, FT-IR, EPR, MALDI-TOF mass spectrometry and single crystal X-ray analysis. Porphyrin 1 has a nonplanar structure as indicated by its X-ray structure, DFT and electrochemical studies. 1 was analyzed for its catalytic application in the epoxidation of various alkenes. The catalytic reactions were carried out in CH3CN/H2O mixture in 3 : 1 (v/v) ratio. 1 displayed good efficiency in terms of mild reaction conditions, lower reaction temperature and minimal catalyst amount consumption. 1 exhibited excellent selectivity, high conversion efficiency and huge TOF (7600-9800 h-1) in a significantly low reaction time of 0.5 h. Catalyst 1 was regenerated at the end of various catalytic cycles making it reusable and industrially important.