Crystal Growth of new charge-transfer salts based on $\pi$-conjugated molecules

TL;DR

This paper reports the synthesis, structural analysis, and charge transfer investigation of new charge transfer salts based on π-conjugated molecules, providing insights into their growth conditions and electronic interactions.

Contribution

It introduces new charge transfer salts with detailed structural characterization and systematic analysis of charge transfer using various acceptor strengths and donor molecules.

Findings

Crystal structures determined by X-ray diffraction.

Growth conditions affect crystal size and quality.

Charge transfer analyzed via geometry and infrared spectroscopy.

Abstract

New charge transfer crystals of $\pi$-conjugated, aromatic molecules (phenanthrene and picene) as donors were obtained by physical vapor transport. The melting behavior, optimization of crystal growth and the crystal structure is reported for charge transfer salts with (fluorinated) tetracyanoquinodimethane (TCNQ-F$_x$, x=0, 2, 4), which was used as acceptor material. The crystal structures were determined by single-crystal X-ray diffraction. Growth conditions for different vapor pressures in closed ampules were applied and the effect of these starting conditions for crystal size and quality is reported. The process of charge transfer was investigated by geometrical analysis of the crystal structure and by infrared spectroscopy on single crystals. With these three different acceptor strengths and the two sets of donor materials, it is possible to investigate the distribution of the charge transfer systematically. This helps to understand the charge transfer process in this class of materials with $\pi$-conjugated donor molecules.