Study of Judd-Ofelt, Urbach energy and photosensitization process in luminescent Sm(III) complexes with heterocyclic ligands.

Six samarium (III) complexes were synthesised by employing the ß-ketocarboxylic acid as main ligand and five N-donor systems as ancillary ligands through the environmentally safe liquid-assisted grinding method. Various characterisation techniques were employed to determine the structure of the complexes i.e. NMR, IR, XRD and SEM. Photoluminescent studies were carried out in solid as well as in solution form. In solid and solution form emission spectra show maximum intensity peak at 604 and 602 nm, respectively, assigned to 4G5/2 → 6H7/2 transition which explains orange emission on UV excitation in complexes. CCT, CP, colorimetric parameters and quantum yield (relative and intrinsic) of the synthesized complexes were calculated. With the help of reflectance spectra, band gap and Urbach energy were determined. Lasing parameters were also calculated by employing FWHM values obtained from Gaussian fitting. Energy transfer study revealed the efficacious energy transfer from ligand to metal's emissive level. Further antimicrobial studies revealed higher activity in case of complexes in comparison to ligand.

Computational and optoelectronic quantification of semi-conducting, warm ruby red color emanating Eu3+ complexes with hetro-cyclic ligands.

Six Eu3+ complexes were synthesised with ß-keto acid as main ligand and secondary ligands through liquid assisted grinding method. These complexes were characterised by various techniques such as spectroscopic technique, XRD, EDAX, SEM analysis, thermal technique, Urbach energy and optical band gap investigation. The luminous photophysical properties were studied by PL spectroscopy in solid as well as solution phase and some theoretical calculation was done to investigate the radiative (Arad) & non-radiative (Anrad) transition rate, quantum efficiency (ɸ), Judd Ofelt parameters for 5D0 → 7F2,4 transitions in both states. Judd Ofelt parameters were also calculated by the JOES software and the outcomes are well harmonised with theoretical values. The complexes have CIE color coordinate value in ruby red region and above 88.65% color purity in both phases, which made them attractive candidates for red light-emitting displays. 5D0 → 7F2 transition was proposed as a laser emission transition owing to their high branching ratio (67.18-74.24%) in solid and (60.09-74.40%) in solution phase. Computational methods were employed to determine the structure and energy of various molecular orbitals. Antimicrobial assay of complexes was also rationalised and found that the complexes are pertinent as good bactericidal and fungicidal agents in pharmaceutical industry.

Augmentation of photophysical features and Judd-Ofelt analysis of extensively green glowing terbium (III) complexes with nitrogen donor ancillary ligands.

Six green glowing terbium (III) complexes were fabricated via grinding method utilizing a prime organic ligand (L) and nitrogen donor ancillary ligands. Characterization of synthesized complexes was accomplished through various spectroscopic techniques. The significant thermal stability was determined by thermogravimetric analysis while the energy bandgap and Urbach energy were investigated through diffused reflectance spectra of these complexes. The peak observed at 548 nm in emission spectra is responsible for the virescent color of these complexes. Color purity, decay time, quantum yield, and emission intensities of ternary complexes were significantly improved as compared to binary ones due to the synergistic effect of ancillary ligands. Judd-Ofelt parameters were determined by the NIR absorption spectrum, which claims the asymmetric environment around the terbium (III) ion. CCT values advocate the applicability of these complexes in green light-emitting materials as a cool light source. The biological assignments reveal the significance of these complexes as potent antioxidants and antimicrobial agents. The energy transfer process highlights the enhancement of luminescence in these complexes via the synergic effect of ligands. Our investigation portrays that these complexes can be employed in laser technology, display devices, semiconductors, biological fields, and optoelectronic devices.

Applicability of Reddish-Orange Light Emitting Samarium (III) Complexes for Biomedical and Multifunctional Optoelectronic Devices.

Six crimson samarium (III) complexes based on ß-ketone carboxylic acid and ancillary ligands were synthesized by adopting the grinding technique. All synthesized complexes were investigated via elemental analysis, infrared, UV-Vis, NMR, TG/DTG and photoluminescence studies. Optical properties of these photostimulated samarium (III) complexes exhibit reddish-orange luminescence due to 4G5/2 → 6H7/2 electronic transition at 606 nm of samarium (III) ions. Further, energy bandgap, color purity, CIE color coordinates, CCT and quantum yield of all complexes were determined accurately. Replacement of water molecules by ancillary ligands enriched these complexes (S2-S6) with decay time, quantum yield, luminescence, energy bandgap and biological properties than parent complex (S1). Interestingly, these efficient properties of complexes may find their applications in optoelectronics and lighting systems. In addition to these, the antioxidant and antimicrobial assays were also investigated to explore the applications in biological assays.

Strategies in synthetic design and structure-activity relationship studies of novel heterocyclic scaffolds as aldose reductase-2 inhibitors.

Heterocyclic scaffolds of natural as well as synthetic origin provide almost all categories of drugs exhibiting a wide range of pharmacological activities, such as antibiotics, antidiabetic and anticancer agents, and so on. Under normal homeostasis, aldose reductase 2 (ALR2) regulates vital metabolic functions; however, in pathological conditions like diabetes, ALR2 is unable to function and leads to secondary diabetic complications. ALR2 inhibitors are a novel target for the treatment of retinopathy (cataract) influenced by diabetes. Epalrestat (stat), an ALR2 inhibitor, is the only drug candidate that was approved in the last four decades; the other drugs from the stat class were retracted after clinical trial studies due to untoward iatrogenic effects. The present study summarizes the recent development (2014 and onwards) of this pharmacologically active ALR2 heterocyclic scaffold and illustrates the rationale behind the design, structure-activity relationships, and biological studies performed on these molecules. The aim of the current review is to pave a straight path for medicinal chemists and chemical biologists, and, in general, to the drug discovery scientists to facilitate the synthesis and development of novel ALR2 inhibitors that may serve as lead molecules for the treatment of diseases related to the ALR2 enzyme.

Designing of emerald terbium (III) ions with ß-ketocarboxylic acid and heterocyclic ancillary ligands for biological and optoelectronic applications.

A green and highly efficient grinding method was adopted to synthesize emerald terbium complexes with 1-cyclopropyl-6-fluro-4-oxo-7-piperazin-1-ylquinoline-3-carboxylic acid as the main organic ligand and 2,2'-bipyridyl, 1,10-phenanthroline, neocuproine, 5,6-dimethyl-1,10-phenanthroline and bathophenanthroline as ancillary ligands. Structural analysis of these complexes was executed via elemental, infrared and 1 H-nuclear magnetic resonance analysis, which confirmed that the ligand coordinated to the metal ion through ß-ketone and hydroxyl groups of carboxylic acid. Thermal stability of these complexes was investigated by study of thermogravimetric/derivative thermogravimetric analysis. Photoluminescence properties were investigated by observing emission spectra (400-700 nm), excitation spectra (250-500 nm) and decay time curves for display devices. The emission spectra revealed that an intense peak at 545 nm was observed due to 5 D4 →7 F5 electronic transition, which is responsible for the emerald colour in synthesized complexes, under 353 nm ultraviolet light excitation. The energy band gap and refractive index were determined, which proclaimed the dormant applications of these complexes in semiconductors. Commission Internationale de l'éclairage colour coordinates confirmed that the emerald emission of these complexes lies in the green region. Furthermore, antioxidant, antimicrobial and antimalarial assays of these complexes were also investigated, which confirmed that these complexes are potent for antioxidant, antimicrobial and antimalarial activities.