Lasing Properties Activation by Constitutional Isomerism of an Electron-Accepting Group

Abstract

Materials engineering plays a pivotal role considering its manifold applications, i.e., in medicine as individualized drug carriers or in advanced technologies such as optoelectronic devices and others. Recently, increasing interest in the pyrazoline derivatives family of compounds was noticed. In this paper, we report on the constitutional isomerism influence on photophysical properties of low molecular, push-pull type of pyrazole-based organic chromophores. Particularly, we show the ability of optical properties tailoring by changing the substitution of phenyl ring extended by effective electron-accepting moiety in ortho and para positions. Such a structural change in molecule results in a shift of photoluminescence spectra as well as the activation or deactivation of gain mechanism for multimode laser emission. In order to confirm ground state molecular structures for both isomers we performed time-dependent DFT calculations in a solvent environment. In addition, structural analysis of spontaneously grown single crystals was carried out using X-ray spectroscopy. The above-mentioned studies allowed us to define the isomer's molecular geometries and charge distribution in excited and ground states and to distinguish the significant differences in crystallographic structures. Combined experimental and theoretical research have resulted in a hypothesis of the molecular mechanism standing behind observed differences in optical properties of both isomers. Importantly, such an approach can be useful for materials engineering, allowing us to predict the features of novel materials for optoelectronics and photonics.