Photophysics of Schiff Bases: Theoretical Study of Salicylidene Methylamine

Abstract

The proton-transfer reaction in a model aromatic Schiff base, salicylidene methylamine (SMA), in the ground and in the lowest electronically-excited singlet states, is theoretically analyzed with the aid of second-order approximate coupled-cluster model CC2, time-dependent density functional theory (TD-DFT) using the Becke, three-parameter Lee-Yang-Parr (B3LYP) functional, and complete active space perturbation theory CASPT2 electronic structure methods. Computed vertical-absorption spectra for the stable ground-state isomers of SMA fully confirm the photochromism of SMA. The potential-energy profiles of the ground and the lowest excited singlet state are calculated and four photophysically relevant isomeric forms of SMA; α, β, γ, and δ are discussed. The calculations indicate two S(1)/S(0) conical intersections which provide non-adiabatic gates for a radiationless decay to the ground state. The photophysical scheme which emerges from the theoretical study is related to recent experimental results obtained for SMA and its derivatives in the low-temperature argon matrices (J. Grzegorzek, A. Filarowski, Z. Mielke, Phys. Chem. Chem. Phys. 2011, 13, 16596-16605). Our results suggest that aromatic Schiff bases are potential candidates for optically driven molecular switches.

Excited‐State Intramolecular Proton Transfer: Photoswitching in Salicylidene Methylamine Derivatives

“…In geometry optimization Scheme 1. [27] and the Supporting Information). and reaction-path calculations, the correlation-consistent split valence double zeta basis set with polarization functions on all atoms (cc-pVDZ) was used.…”

“…[5] Over the years, most research effort in this field has been focused on two classes of intramolecular reactions related to photochromism. [11][12][23][24][25][26][27] A qualitative photophysical scheme for optically driven molecular switches based on the ESIPT phenomenon was proposed by us recently. [9 and 10]).…”

Photochromic cycle of 2′-hydroxyacetophenone azine studied by absorption and emission spectroscopy in different solvents

“…The theoretical studies by quantum mechanical and semi-empirical methods of the ground and excited states are presented in a number of papers. [15][16][17][18][19][20][21] It should be stressed that one of the main aims of the present study is to investigate the effect of the strength of intramolecular hydrogen bond on the photochromic cycle of azine derivatives of Schiff bases by comparison of the results for 2 -hydroxyacetophenone azine (APA) with those previously obtained for salicyaldehyde azine (SAA). 22 …”

Optical and electrochemical properties of novel thermally stable Schiff bases bearing naphthalene unit

“…Small molecules have the advantage over polymers because they exhibit well-defined molecular structure, molecular weight without any distribution and can be easy purified. Schiff bases demonstrated the potential application as optically driven molecular switches [13][14], luminescent and pH indicators [15], electrochromic and photochromic materials [16][17][18].…”