Ferromagnetic interactions through end-on azido bridges in a nickel(II) dimer: [Ni/sub 2/(C/sub 15/H/sub 11/N/sub 3/)/sub 2/(H/sub 2/O)(N/sub 3/)/sub 3/]ClO/sub 4/.H/sub 2/O

Abstract

The crystal structure of [Ni/sub 2/(C/sub 15/H/sub 11/N/sub 3/)/sub 2/-(H/sub 2/O)(N/sub 3/)/sub 3/]ClO/sub 4/.H/sub 2/O, (C/sub 15/H/sub 11/N/sub 3/)=2,2':6', 2"-terpyride, has been solved: a=10.179(2), b=10.800(3), c=16.866(6) /spl Aring/, /spl alpha/=85.54(2), /spl beta/=78.49(2), /spl gamma/=72.03(1)/spl deg/, R=0.055, R/sub W/=0.061. It consists of dimeric cations where the two nickel(II) ions are linked through the nitrogen atoms of two azide bridging groups in end-on fashion and ClO/sub 4/-anions. Magnetic susceptibility measurements show the existence of ferromagnetic superexchange between the nickel ions. The exchange parameters determined are J=+13.6 cm/sup -1/, D=-19.2 cm(-1), Z'J'=0.03 cm/sup -1/ and g=2.12. Q-band EPR spectrum shows signals at 525 and 1100 mT values. A theoretical study, by using extended Huckel molecular orbital calculations, shows a minimum of the antiferromagnetic component of the exchange parameter for a bridging angle of 115/spl deg/.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>