Paramasivan Rajasingh

By incorporating Furfural-Antipyrine as coordinate sites into the fragment of receptor FBH-AP has been used as an artificial chemosensor for selective recognition of transition metals. The strong fluorescence emission at 388 nm of the receptor FBH-AP is effectively and selectively quenched by Al3+. A 1:1 complex is formed between the FBH-AP and Al3+ is determined by jobs plot and their common interferent ions do not show any interference with the Al3+. It is anticipated that the antipyrine could be a good candidate probe and has potential application for Al3+ determination.

The hydrothermal method was used to synthesize hexagonal 3-5 nm CdS QDs with Delonix elata leaves aqueous extract as a capping agent. The synthesized CdS QDs were characterized by FTIR, UV-Vis, XRD, FESEM spectroscopy. The anticorrosion activity of CdS QDs coated Zn plate was exanimated under 1 M HCl, 6 M KOH, 3.5% NaCl electrolytic medium. The best corrosion resistance was achieved through the application of the CdS QDs coating on the Zn metal surface.

A simple antipyrine based dyad system HMIP was designed and synthesized from 4-aminoanitpyrine and substituted isophthalaldehyde for selective detection of Cu²⁺ ions through fluorescent quenching mechanism in acetonitrile medium at pH 7. The fluorescent sensor showed a 1:1 stoichiometry with Cu²⁺ ions obtained through Job's plot analysis. The fluorescence turn "OFF" behaviour of HMIP was attributed towards ligand-to-metal charge transfer mechanism. The quenching constant was calculated as 1.29 × 10⁴ M^–1 and the sensor was also found to be reversible with EDTA solution.

The synthesis of 3‐heteroaryl‐substituted tetrahydrofurans from the propargyl derivative of Baylis–Hillman adducts of heteroaryl aldehydes by n‐Bu₃SnH‐mediated 5‐exo‐trig vinyl radical cyclization in high yield is reported.

A novel method for the bromination of perylene diimides, PDI (1), under mild conditions is reported. Variation of the reaction conditions allows mono- and dibromination of PDIs to afford 2 and 3 (these can be separated through standard procedures) or exclusive dibromination to afford 3. Pure 1,7 regioisomers are obtained through repetitive crystallization. The structure of 1,7-3b was elucidated by a single-crystal X-ray analysis. The facility of the bromination reaction, which decreases in the order 1a > 1b > 1c, depends on PDI aggregation propensities. Monobrominated PDIs were utilized for the syntheses of novel unsymmetrical piperidinyl (4a and 4b) and trimethylsilylethynyl derivatives (5a and 5b). Computational studies (DFT) on imide substituent rotation in PDIs reveal that in the case of bulky groups there is a restricted rotation leading to isomers, in agreement with our experimental results. An aromatic core twist in PDIs bearing one and two bromine substituents was also investigated by DFT.