Semiconducting, magnetic, luminescence properties and theoretical calculations of the tetra-azamacrocyclic compound: trans-Cr(cyclam)Cl2]TCNQ

Abstract We report the new macrocyclic compound: trans -[Cr( RSSR -cyclam)Cl 2 ]TCNQ·H 2 O (1) , (where cyclam: 1,4,8,11-tetraazacyclotetradecane and TCNQ: 7,7,8,8-tetracyanoquinodimethane). Its 3D structure showed π-π interactions between the TCNQ − moieties with alternating distances (3.24 and 3.87 A). 1 exhibited an electric conductivity, σ  = 1.94 × 10 −5  Scm −1 at 300 K and a band-gap of 0.53 eV in the range of a semiconductor. Its magnetic behavior is of a typical Curie–Weiss paramagnet with an antiferromagnetic coupling ( θ  = −15 K). The measured magnetic moment, μ exp  = 3.84 B. M. at room temperature is lower than the expected, μ calc  = 4.86 B. M. (only spin) for a d 3 octahedral chromium (III) and an anionic radical TCNQ − ; this is explained by the presence of diamagnetic dimers of TCNQ − in the crystal packing. 1 shows photoluminescence at low temperature from 80-17 K. Finally, by using DFT calculations, it was possible to assign van der Waals (CH–π, Cl–π) interactions and N–H hydrogen bonding, which are likely determining the observed antiferromagnetism. The calculations also allowed us to verify the presence of diamagnetic dimers in the crystal packing, formed by strong π–π interactions of TCNQ-entities.