Explicit Spectral Response of the Geometrical Isomers of a Bio-Active Pyrazoline Derivative Encapsulated in β‑Cyclodextrin Nanocavity: A Photophysical and Quantum Chemical Analysis

• Published in: The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Vol. 116; no. 42; pp. 10371 - 10382
• Main Authors: Mati, Soumya Sundar, Sarkar, Sunandan, Sarkar, Pranab, Bhattacharya, Subhash Chandra
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 25.10.2012
• Subjects: beta-Cyclodextrins - chemistry; Derivatives; Encapsulation; Grounds; Isomers; Mathematical analysis; Models, Molecular; Molecular Structure; Nanostructure; Nanostructures - chemistry; Photochemical Processes; Polarity; Pyrazoles - chemistry; Quantum Theory; Solvents; Spectrometry, Fluorescence; Spectrophotometry, Ultraviolet; Stereoisomerism
• ISSN: 1089-5639; 1520-5215
• DOI: 10.1021/jp307964z

The existence of two geometrical isomers (cis- and trans-) of a biologically significant pyrazoline derivative [5-(-1′-(4-bromo-phenyl)-3a′,7a′-hexahydro-1′H-indazol-3′-yl)-3-methyl-1-phenyl-1H-pyrazole-4-carbonitrile] (PZ) has been established using a combined theoretical and experimental investigation. Solvatochromic analysis of PZ revealed the existence of said cis- and trans- isomers. The unique solvatochromic response of the PZ isomers and their preferential encapsulation within β-cyclodextrin (β-CD) nanocavity clearly shows the difference in the behavioral nature of the isomers of PZ in homogeneous and heterogeneous medium. Solvent polarity, time-resolved study, and anisotropy results also reinforce in favor of the existence of the isomers. To evaluate the actual orientation of cis and trans-PZ, the ground and excited state geometry of these isomers were optimized by the DFT/LanL2DZ and CIS/LanL2DZ methods, respectively. The experimentally observed results and the theoretically calculated results are found to be in close agreement.