Magneto-structural and theoretical study of the weak interactions in a Mn(II) complex with a very unusual N,O-chelating coordination mode of 2-aminoterephthalate

The Mn(II) complex [Mn(atpa)(H2O)2]·H2On (1),with the dicarboxylate ligand 2-aminoterephthalic acid (H2atpa), has been synthesized and crystallographically, spectroscopically and magnetically characterized. Complex 1 shows a very unusual 1κ2N,O coordination mode of the aminoterephthalate dianion with the Mn(II) ion. One of the carboxylate groups shows a syn-anti-μ2-η1:η1 binding mode to form a 2D square grid. The magnetic properties of this compound can be very well reproduced with a regular S = 5/2 chain model with a very weak antiferromagnetic coupling constant of J = −0.2 cm−1 through the single syn-anti carboxylate bridges. EPR measurement also supports the experimental data obtained from the magnetic study. The influence of the torsion angle between the carboxylate groups on the various interaction energies of 1 is calculated by means of DFT study.