Tetramethyltetrathiafulvalene [(NbOF)]: One-Dimensional Charge Transfer Salt with an Infinite Anion Chain.

An unusual valence one-dimensional (1D) molecular charge transfer salt (TMTTF)(NbOF) [TMTTF = tetramethyltetrathiafulvalene] with infinite anion chains was prepared. To understand the crystal structure and electronic states of the (TMTTF)(NbOF) salt, we performed synchrotron X-ray diffraction, electron spin resonance, and static magnetization measurements. There is only one independent TMTTF molecule in the unit cell of (TMTTF)(NbOF). The TMTTF cation radicals stack to form 1D columns. The effective charge of the TMTTF molecule in the crystal was estimated to be +1. The electric charge of TMTTF donors is compensated by the infinite anion chains [(NbOF)]. The magnetic susceptibility of (TMTTF)(NbOF) is 4 × 10 emu/mol at room temperature and shows weak temperature dependence above 60 K. However, some deviation appears below 60 K. The temperature dependence of the spin susceptibility shows a noticeable enhancement below 60 K. Below 5 K, the magnetization curve as a function of the magnetic field deviates from the straight line and shows a saturation tendency. The experimental results can be reproduced well with the = 2 spin system at 2 K. The detailed analysis of the crystal structure and anomalous low-temperature magnetic state magnetic properties of (TMTTF)(NbOF) are discussed.