H-bonded supramolecular synthon induced magnetic superexchange phenomenon results weak ferromagnetic and strong antiferromagnetic interactions in two new copper-orotate coordination network.

Hydrothermal self-assembly of orotic acid (C 5 H 4 N 2 O 4 OrH 3 ) with metal salt Cu(Ac) 2 ·H 2 O yielded a new OrH based hydrogen bonded coordination network of formula [Cu(OrH)(2NH 3 )(H 2 O)]·H 2 O ( 1 ) and [Cu(OrH) (2NH 3 )] 2 ( 2 ). Single crystal X–ray study on 1 confirms that +2 charges on the metal ions (Cu 2+ ) are balanced by OrH anion. N–H⋯O and O–H⋯O hydrogen bonding synthons are the only artifact for the resulting hydrogen bonded copper-OrH architecture. Temperature dependent measurements of magnetic susceptibility reveals the occurrence of competitive exchange interactions with a net ferromagnetic character in 1 ( J  = +0.48 cm −1 ) and strong antiferromagnetic interaction in 2 ( J  = −4.93 cm −1 ). Magnetic superexchange interaction transmitted through equatorial–axial hydrogen bridge system promotes weak ferromagnetic interactions in 1 while in 2 it is in basal-basal position, in which two d x2-y2 orbitals is involved in exchange mechanism reveals the coexistence of two antiferromagnetic exchange pathways, intramolecular much stronger than intermolecular. The natural bond orbital (NBO) analysis applied separately to α and β spin density matrices clearly shows two important magnetic superexchange pathway with shorter Cu⋯Cu contact 5.542(4) Å and 4.845(4) Å or 5.755(1) Å in ( 1 ) and inter dimer 6.665(1) Å and 4.6744(9) Å for ( 2 ). [ABSTRACT FROM AUTHOR]