Modulating Magnetic and Photoluminescence Properties in 2-aminonicotinate based Bifunctional Coordination Polymers by Merging 3d-Metal Ions.

Herein, we report the synthesis and study of bifunctional coordination polymers (CPs) with both, magnetic and photoluminescence properties derived from a heterometallic environment. As a starting point, three isostructural monometallic CPs with [M(μ-2ani)2]n [M(II) = Mn (1Mn), Co (3Co) and Ni (4Ni), 2ani = 2-aminonicotinate] formula, crystallize as chiral 2D-layered structures stacked by means of supramolecular interactions. These compounds show high thermal stability in solid state (above 350 oC), despite of which 1Mn in aqueous solution is shown to partially transform into a novel 1D chained CP with [Mn(2ani)2(μ-H2O)2]n (2Mn) formula. A consistent study of the dc magnetic properties of 1Mn, 3Co and 4Ni reveal a spin-canted structure deriving from antisymmetric antiferromagnetic weak exchanges along the chiral network (as confirmed by DFT calculations) and magnetic anisotropy of the ions, in such a way that the long-range ordering is observed with variable magnitude for the spin carriers. Moreover, 3Co and 4Ni show no frequency-dependent ac susceptibility curves under zero dc field, a characteristic behaviour of a glassy state that may be partially supressed for 3Co by applying an external dc field. To overcome the long-range magnetic ordering, Co(II) ions are diluted in a diamagnetic Zn(II)-based matrix, which enables the single-molecule magnet (SMM) behaviour. Interestingly, this strategy allows obtaining a bifunctional CoxZn1-x2ani material being imbued with a strong photoluminescent emitting capacity characterized by an intense blue light followed by a green afterglow.