Optical and magnetic properties of trans-indigo˙− radical anions. Magnetic coupling between trans-indigo˙− (S = 1/2) mediated by intermolecular hydrogen N–H⋯OC bonds†
Abstract
The radical anion salt {cryptand[2.2.2](K+)}6{trans-indigo}7·5.5C6H4Cl2 (1) with a non-integer negative charge on indigo (−0.86 per molecule on average) was obtained. The salt manifests an effective magnetic moment of 1.59 μB at 300 K and strong enough antiferromagnetic coupling of spins to be mediated by intermolecular hydrogen bonds.