From Low-Dimensional Manganese(II) Azido Motifs to Higher-Dimensional Materials: Structure and Magnetic Properties

Four new inorganic−organic hybrid coordination polymers in which 1D or 2D manganese(II) azido inorganic motifs
are interlinked into higher-dimensional networks have been synthesized by use of a series of bis(pyridyl)-type
organic bridging ligands (linkers) with different side groups and/or different coordination orientations. The dimensionality
and the topology of the manganese(II) azido motif and the whole structure are sensitive to the organic linkers
used. Compounds 1 and 3 are 3D coordination polymers with pillared-layer architectures:  in 1, 2D Mn(II) layers
with alternate double end-on (EO) and single end-to-end (EE) azido bridges are pillared by zigzag organic linkers,
and 3 is built from single EE azido-bridged Mn(II) layers and linear organic linkers. The 3D nets of 1, 3, and related
compounds have been related to the specific length and coordination orientation of the organic pillars and the
undulate shape of the manganese(II) azido layers. Consistent with their structures, both 1 and 3 exhibit weak
ferromagnetism due to spin canting. Compound 1 is a weak ferromagnet with Tc = 16 K, and 3 is a metamagnet
with Tc = 23 K. On the other hand, compounds 2 and 4 are 2D coordination networks in which 1D manganese(II)
azido chains are interlinked by organic linkers:  2 is the first 2D network built from Mn(II) chains with alternate
double EE and double EO azido bridges, which mediate antiferro- and ferromagnetic interactions, respectively; 4
is the first 2D network built from Mn(II) chains with only single EE azido bridges, which mediate antiferromagnetic
interactions. The magnetic susceptibility of 4 exhibits a rapid rise at very low temperature, which may be attributed
to paramagnetic impurities or spin canting.