This review covers few examples of anion complexation chemistry, with a special focus on urea/thiourea-based receptors and Zn(II)-dipicolyl amine-based receptors. This article specially focuses on structural aspects of the receptors and the anions for obtaining the desire specificity along with an efficient receptor-anion interaction. Two types of receptors have been described in this brief account; first one being the strong hydrogen bond donor urea/thiourea derivatives, which binds the anionic analytes through hydrogen bonded interactions; while, the second type of receptors are coordination complexes, where the coordination of the anion to the metal centre. In both the cases the anion binding modulate the energy gap between the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) and thereby the spectroscopic response. Appropriate choice of the signalling unit may allow probing the anion binding phenomena through visual detection.

A new nickel(II) complex [Ni(L)] (1) [H₂L = 1,1′-(1E,1′E)-(propane-1,3-diylbis(azan-1-yl-1-ylidene))bis(methan-1-yl-1-ylidene)dinaphthalen-2-ol] was synthesized and X-ray crystallographically characterized. 1 crystallizes in orthorhombic crystal system with Cmc21 space group. The unit cell dimensions of the crystal are a = 30.6345(4)Å, b = 8.45340(10)Å, c = 7.75180(10)Å. Structural analysis reveals a tetradentate chelation behaviour of the dianionic ligand H₂L having a distorted square planar geometry around Ni(II) with NiN₂O₂ chromophore in 1. The title complex 1 behaves as an effective catalyst towards oxidation of 3,5-ditertiarybutyl catechol (3,5-DTBC) in acetonitrile to its corresponding quinone derivative in air. The reaction follows first-order reaction kinetics with rate constant 4.28 × 10⁻⁵ min^-1. The reaction follows Michaelis-Menten enzymatic kinetics with a turnover number of ($K_{cat}$) 140.72 h^-1 in acetonitrile.

Synthesis of a functionalized tricyclo[6.2.0.0^2,6]decane derivative in enantiomerically pure form, the core structure present in the natural products kelsoene and poduran, is described. The key steps involve a stereocontrolled copper (I)-catalyzed intramolecular [2+2] photocycloaddition of a 1, 6-diene prepared from D-mannitol to form a substituted bicyclo[3.2.0]heptane derivative and a ring closing olefin metathesis involving the vicinal substituents on the five-membered ring of the bicyclo[3.2.0]heptane derivative.