This article presents a brief overview of the reactions of2,4,6-tris(2-pyridyl)-1,3,5-triazine (tptz) in presence of rhodium(III), ruthenium(II) and osmium(II) under various experimental conditions. Under certain experimental conditions tptz exhibits metal-assisted hydrolysis/hydroxylation at the triazine ring. However, synthetic methods have also been developed to prepare complexes with intact tptz. Molecular structures of some of the complexes, especially stereoisomers of the hydroxylated products, are established by single crystal X-ray studies. A critical analysis of all data suggests that the electron-withdrawing effect of the metal ion (L→Mσ donation) is the predominant factor, rather than angular strain, that is responsible for metal-promoted reactivities. Electrochemical properties of all of these complexes have been investigated, Rh(III) complexes are excellent catalysts for electrocatalytic reduction of CO₂, and dinuclear Ru(II) and Os(II) complexes exhibit strong electronic communication between the metal centres.

Constituents of urinary stones obtained from various patients from western part of India, which is a highly urinary stone disease-prone area, have been analysed. Eight stones from four patients were collected through urologists and have been analysed using powder X-ray diffraction and FT-IR. Thermogravimetric analysis (TGA) and scanning electron microscopic (SEM) image of selected samples were also carried out. The analysis revealed that calcium oxalate monohydrate, which is also known as whewellite, is the common constituent of all of the stones, particularly at the initial stage of stone formation. However, multi phases viz. whewellite phase, and hydroxyl and carbonate apatite phases are also detected in the case of third and fourth patients, from where multiple stones were obtained. Interestingly, in these mixed phase stones the concentration of whewellite decreases with increasing the concentration of apatite phases. Thermal behaviour of the whewellite phase was studied by TGA and variable temperature XRD analysis. Morphology of the whewellite and apatite phases, examined by SEM image, has also been reported.

This article presents a brief account on designing of calixarene-based molecular sensor for recognition of various metal ions and anions and also different analytical techniques to monitor the recognition event. This review focuses only on calix[4]arene derivatives, in which mainly the lower rim is modified incorporating either crown moiety to make calix-crown hybrid ionophore to encapsulate metal ions or some fluoregenic inorganic and organic moieties to use it as signalling unit. In order to investigate effect of conformation of the calixarene unit and steric crowding on ion selectivity, designing of these molecules have been made using both the cone and 1,3-alternate conformations of the calixarene unit and also incorporating bulky tert-butyl group in few cases to impose controlled steric crowding. Among various ions, here focuses are mainly on biologically and commercially important alkali metal ion such as K⁺, toxic metal ions such as Hg²⁺, Pb²⁺, Cd²⁺, important transition metal ion such as Cu²⁺ and toxic anion like F⁻. The techniques used to monitor the recognition event and also to determine binding constants with strongly interacting ions are fluorescence, UV-vis and ¹H NMR spectroscopy. Most of the ionophores reported in this review have been characterized crystallographically, however no structural information (except one case) are incorporated in this article, as it will occupy space without significant enhancement of chemistry part. Different factors such as size of the ionophore cavity, size of metal ion, coordination sites/donor atoms, steric crowding and solvents, which determine selectivity have been discussed. Response of ion recognition process to different analytical techniques is another interesting factor discussed in this article.

Calixarene functionalized gold nanoparticles (CFAuNPs) have been prepared and characterized by spectroscopic and microscopic (TEM) techniques. To use this material as potential colorimetric sensor, the binding property of this new material has been investigated with a large number of metal ions. It exhibited sharp colour change from dark brown to green and blue, detectable by naked-eye, in the presence of Cu²⁺ and Pb²⁺ ions, respectively. It has also triggered substantial change in surface plasmon resonance (SPR) band of the functionalized gold nanoparticles, which in case of Pb(II) is due to the inter particle plasmon coupling arising from the metal-induced aggregation of the nanoparticles and for Cu(II), it is because of the formation of AuCu alloy due to anti-galvanic exchange. The size and aggregation of the nanoparticles are confirmed from HRTEM images, elemental analysis and the line profiling for both the metal ions have been done by STEM-EDX analysis.

New pseudopolymorph of a O,N,N′-donor hydrazone ligand, 2-pyridylcarboxaldehyde isonicotinoylhydrazone (L) and its discrete complexes with K⁺ and Ba²⁺ have been reported. L forms isostructural dinuclear complexes with K⁺ when bromide and iodide were employed as counter anions. However, a monomeric complex in the case of Ba²⁺ with existence of coordinated as well as lattice perchlorate counter anions was observed. All compounds were characterized by single crystal X-ray analysis and other physicochemical techniques. Structural analysis and spectral features of all compounds are described in detail.