[Mo^VIO₂(S₂C₂(CN)₂)₂]₂₋ (┘1) and [Mo^IVO(S₂C₂(CN)₂)₂]²⁻ (2) mimick oxidoreductase enzymatic activities of sulphite oxidase with biological electron donor, SO₃²⁻, andin vitro electron acceptor, [Fe(CN)₆]³⁻, demonstrating proton coupled electron transfer reaction in water and inhibition of the oxidation of (2) in the presence of KCN. The sulphite exidizing system is characterized by substrate saturation kinetics indicating the biological significance of the reactions

(NEt₄)₂[W^IVO(S₂C₂(CN)₂)₂] (1), isolated by reaction of Na₂ WO₄, Na₂S₂C₂(CN)₂ (Na₂mnt) in acidified (pH5.5) aqueous medium in the presence of excess of sodium dithionite and NEt₄Br, reduces CO₂/HCO₃⁻ (pH 7.5) to yield HCOO⁻ and (NEt₄)₂[W^VIO₂(S₂C₂(CN)₂)₂] (2) mimicking tungsten-formate dehydrogenase (W-FDH) activity. (1) reacts with Na₂MoO₄ in acidic medium to produce [Mo^IvO(S₂C₂(CN)₂)₂]²⁻ implicating the displacement of tungsten by molybdenum from the cofactor complex in W-FDH.

[W(CO)₃(η⁶-C₆₀)] has been synthesized by sunlight irradiation of a benzene solution of C₆₀ and W(CO)₆ or [W(CO)₃(η⁶-C₆H₆)] as a red-brown solid. This compound has been characterized by elemental analysis and by FAB mass spectroscopy (parent ion peak centred at 988 (30%)). Chemical reactivity and IR spectroscopy indicate a hexahapto mode of bonding in this complex according to the 18-electron rule. XPS and cyclic voltammetric data support the electron acceptor/donor properties of bonded C₆₀ and the electron donor/acceptor properties of W(CO)₃ moiety respectively in this compound.

The addition of triphenylphosphine (PPh₃), into [Et₄N]₄[Cu₄(mnt)₄] shifted its characteristic electronic spectral band at 377 nm to 372 nm which is identical to that of the monomeric species, [Et₄N][Cu(mnt)(PPh₃)]. This reaction was followed by electrochemical study and also by ³¹P NMR spectroscopy. Such interconversion with the participation of breaking of bridging copper-$\mu_3$-sulfur bond with the formation of new copper-phosphorous bond led to the development of a catalytic cycle using excess PPh₃ and S or Se as the reacting substrates. The turnover number for the oxidation of PPh₃ by S was found to be $0.8 \times 10^{-2} s^{-1}$ and that with Se was $0.6 \times 10^{-2} s^{-1}$ using this catalytic system.

Two nitrato-iron(III) porphyrinates [Fe(4-Me-TPP)(NO₃)] 1 and [Fe(4-OMe-TPP)(NO₃)] 2 are reported. Interestingly, [Fe(4-Me-TPP)(NO₃)] 1 has nitrate ion coordinated as monodentate (by single oxygen atom), while [Fe(4-OMe-TPP)(NO₃)] 2 has nitrate coordination through bidentate mode. Compound 1 was found serendipitously in the reaction of [Fe(4-Me-TPP)Cl] with nitrous acid, which was performed for the synthesis of nitro-iron(III) porphyrin, [Fe(4-Me-TPP)NO₂]. The compound 2 was synthesized by passing NO₂ gas through a solution of [Fe(4-OMe-TPP)]₂O. Upon passing NO₂ gas through a solution of a 𝜇-oxo-dimer, [Fe(4-Me-TPP)]₂O also produces 1. It is interesting that in more electron-rich porphyrin 2, binding of the nitrate in a symmetrical bidentate way while in less electron-rich porphyrin 1, binding of the anion is unidentate by a terminal oxygen atom. However, it is expected that the energy difference between the monodentate and bidentate coordination mode is very small and the interchange between these coordination is possible. Upon passing NO₂ gas through a solution of 𝜇-oxo-dimeric iron(III) porphyrin, the nitrato-iron(III) porphyrin forms first, that later gets oxidized to 𝜋-cation radical to yield hydroxy-isoporphyrin in the presence of trace amount of water. These nitrato-iron(III) porphyrinates in moist air slowly converted back to their respective 𝜇-oxo-dimeric iron(III) porphyrins.

A colorimetric and fluorescence turn-off probe 10-(4-azido phenyl)-5,5-difluoro-5h-dipyrrolo[1,2-c:1^¢,2^¢-f][1,3,2] diazaborinin-4-ium-5-uide, 1, for selective detection of H₂S is reported. The probe displayed a robust decrease in fluorescence intensity with high sensitivity, specificity and least toxicity to detect exogenous H2S and also in live normal human oral fibroblast cells loaded with probe 1. The detectionlimit of probe 1 being 0.17 lm for H₂S.