An Old Crystallization Technique as a Fast, Facile, and Adaptable Method for Obtaining Single Crystals of Unstable "LiTCNQF" and New Compounds of TCNQ or TCNQF: Syntheses, Crystal Structures, and Magnetic Properties.

Detailed structural information is essential for understanding the properties of TCNQ and TCNQF compounds (TCNQ = 7,7,8,8-tetracyanoquinodimethane; TCNQF = 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane). The ineludible requirement of obtaining crystals of a size and quality sufficient to yield a successful X-ray diffraction analysis has been challenging to satisfy because of the instability of many of these compounds in solution. Crystals of two new complexes of TCNQ, [-M(2)(TCNQ)] [M = Ni (), Zn (); 2ampy = 2-aminomethylpyridine], as well as unstable [Li(TCNQF)(CHCN)]·CHCN (), can be prepared in minutes by a horizontal diffusion technique and can be harvested easily for X-ray structural studies. Compound , previously described as "LiTCNQF," forms a one-dimensional (1D) ribbon. Compounds and can also be obtained as microcrystalline solids from methanolic solutions of MCl/LiTCNQ/2. Their variable-temperature magnetic studies confirmed a contribution of strongly antiferromagnetically coupled pairs of TCNQ anion radicals at higher temperatures with exchange coupling / = -1206 K and / = -1369 K for and , respectively, estimated using a spin dimer model. The presence of magnetically active anisotropic Ni(II) atoms with = 1 in was confirmed, and the magnetic behavior of , representing an infinite chain of alternating = 1 sites and = 1/2 dimers, was described by a spin-ring model suggesting ferromagnetic exchange coupling between Ni(II) sites and anion radicals.