Modulating the Photochemistry of Bipyridylic Compounds by Symmetric Substitutions

• Published in: Chemphyschem Vol. 11; no. 17; pp. 3696 - 3703
• Main Authors: Ortiz-Sánchez, Juan M., Gelabert, Ricard, Moreno, Miquel, Lluch, José M.
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 03.12.2010; WILEY‐VCH Verlag; Wiley
• Subjects: Chemistry; conical intersections; Exact sciences and technology; excited states; General and physical chemistry; Photochemistry; Physical chemistry of induced reactions (with radiations, particles and ultrasonics); proton transfer; substituent effects; Substituent effect; Nitrogen oxide; Diamine; Diol; Substitution; conical intersections; Fluorine; excited states; Device; Proton transfer; substituent effects; Photochemistry
• ISSN: 1439-4235; 1439-7641
• DOI: 10.1002/cphc.201000596

A quantum electronic study of the effect of substituents on (2,2′‐bipyridyl)‐3,3′‐diol and (2,2′‐bipyridyl)‐3,3′‐diamine is presented. A large difference in the photochemical behavior between the original and the substituted selected systems is expected. For the sake of simplicity, the study is restricted to the symmetrically bi‐substituted compounds: fluorine, the more electronegative atom and thus a strong σ‐acceptor but also a weak π‐donor group, and NO2, a strong π‐acceptor substituent. Among the large set of compounds studied, two receive special attention: 5,5′‐dinitro‐(2,2′‐bipyridyl)‐3,3′‐diamine and 6,6′‐difluoro‐(2,2′‐bipyridyl)‐3,3′‐diol. While in the former case the nitro substitution transforms (2,2′‐bipyridyl)‐3,3′‐diamine, previously suggested to behave as a photomemory material, into a simple fluorescent species, the latter substitution turns (2,2′‐bipyridyl)‐3,3′‐diol into a fresh new candidate for a photomemory device. Modulating photochemistry though substituent effects: Symmetric bisubstitutions on bipyridylic compounds modify the photochemistry by either enhancing or decreasing the probability to obtain a stable photochromic tautomer that can revert to the original form upon irradiation of different wavelength (see scheme).