Different topologies in three manganese-μ-azido 1D compounds: magnetic behavior and DFT-quantum Monte Carlo calculations

Abstract

The syntheses and structural characterization of three new monodimensional azido-bridged manganese(II) complexes with empirical formulae [Mn(N3)2(aminopyz)2]n (1), [Mn(N3)2(4-azpy)2]n (2) and [Mn(N3)2(4-Bzpy)2]n (3) (pyz = pyrazine (1,4-diazine)), 4-azpy = 4-azidopyridine and 4-Bzpy = 4-benzoylpyridine) are reported. 1 is a monodimensional compound with double EO azido bridges, 2 is an alternating monodimensional compound with double end-on and double end-to-end azido bridges in the sequence di-EO-di-EE and 3 is a monodimensional compound with double end-on and double end-to-end azido bridges in the sequence di-EO-di-EO-diEO-di-EO-di-EE. The magnetic properties of 1-3 are reported. Periodic DFT calculations were performed to estimate the J values and quantum Monte Carlo simulations were carried out using the calculated J values to check their accuracy in comparison with the experimental magnetic measurements. From this theoretical analysis, two appealing features of the di-EO Mn(II) compounds can be extracted: first, the exchange coupling becomes more ferromagnetic when the Mn-N-Mn bridging angle becomes larger and the spin density of the bridging nitrogen atoms has an opposite sign to that of the Mn(II) centers