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New inorganic pigments were synthesized through calcination route with advantages such as the ability to prepare homogeneous oxides of lower size, which could provide for higher surface coverage. The synthesized inorganic pigments were characterized by various techniques like infrared, UV-visible spectroscopy and diffuse reflectance spectroscopy (DRS) using CIE -L*a*b* parameters method for colour measurements. The above characterized inorganic pigments were used for the study of the pigments of associated ions. Solid state reactions of these metal ions with transition metal ions like chromium, molybdenum, manganese and iron were carried out individually. A replacement for cadmium, cobalt, lead and mercury based pigments has been sought through the use of rare earth metal ions -cerium and lanthanum. It was found that cerium offered better scope for doping than lanthanum as it produced better shades. Multiple doping plays a vital role in increasing the mass tone and tint strength.

A new UV‐active indole‐pyrazole extended π‐system (probe A) that displays a large bathochromic shift (∼325 nm) when it interacts only with Co2+ and not with other transition metal ions, is presented. The increase in the intensity of new transitions at 592 and 684 nm due to A−Co2+−Cl2.H2O complex formation occurs at the expense of the transition at 358 nm arising from the probe A, and thereby offers a ratiometric method for detection of Co2+ present in aqueous samples. The ratiometric method sets the detection limit for Co2+ at 0.404×10−6 M and 0.337×10−6 M, when calculated for the transitions at 592 and 684 nm, respectively. The corresponding association constants are 4.041×105 M−1 at 592 nm, and 3.617×105 M−1 at 684 nm. Job plot and ESI‐MS data confirmed the 1 : 1 stoichiometry of A−Co2+−Cl2.H2O complex. The mode of interaction between the probe A and Co2+ is explained in terms of conformational isomerization and chelation, using 1H NMR method and DFT calculations. Other metal ions commonly found in the environment do not seem to interfere in the selective determination of Co2+ ions. Suitability of probe A in the detection of Co2+ at concentrations less than 1.7 μM (recommended level of Co2+ ions by US‐EPA) is also demonstrated using water samples collected from the environment. Test kits suitable for routine on‐site analysis are also developed.

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Density functional theoretical calculations predicted non‐coplanar twisted geometry for two new imidazo[1,2‐a]pyridine derivatives, Imp and ImBt. Analysis of single‐crystal of Imp asserted the non‐coplanar twisted geometry, which is implicated in aggregation induced emission (AIE) of small aromatic molecules. Universal quenching by water was observed in aqueous THF solutions of Imp and ImBt, but they showed AIE effect when the water content was more than 80 %. Non‐fluorescent solutions of Imp and ImBt in THF‐water (7 : 3 v/v) mixture turned fluorescent on addition of specific metal ions prompting their potential to be explored for turn‐on sensor applications. While ImBt showed AIE response to Cd2+, Hg2+ and Al3+, Imp displayed AIE effect only to Cd2+ ions, under identical conditions. Absence of interference from common metal ions (including Hg2+ and Al3+) led to selective formation of Imp‐CdCl2 (1 : 1) complex, which offered the limit of detection of Cd2+ to be 19.2 μM. The observed selectivity for Cd2+ permitted the use of Imp in the imaging of live Rhizoctonia oryze contaminated with Cd2+ ions.