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Abstract
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The development of efficient one-pot methodologies for the in situ construction of polydentate N-heterocyclic ligands and their integration into coordination frameworks remains a central challenge in synthetic inorganic chemistry. Herein, we report a one-pot reaction of amino-functionalized pyridine (iso)nicotinoyl hydrazones, thiocyanate, and Mn(II) salts in acetonitrile, which yields two new mixed-ligand Mn(II) coordination complexes, [Mn(HL3)2(NCS)2(H2O)2] (1) and [Mn(HL4)4(NCS)2].CH3CN.0.5(H2O) (2), where HL3 and HL4 represents two in situ formed dipyridyl-1H-1,2,4-triazole ligands. These ligands are formed through a Mn(II)-assisted cyclization of amino-functionalized pyridine (iso)nicotinoyl hydrazone precursors (HL1 and HL2 in acetonitrile). Single-crystal X-ray diffraction confirms the in situ ligand transformation and reveals that both complexes contain six-coordinate Mn(II) centers in distorted octahedral environments, extended through diverse noncovalent interactions into higher-dimensional frameworks. Furthermore, the electronic properties of both complexes 1 and 2 have been demonstrated through theoretical studies based on DFT calculations. Molecular packings of both complexes 1 and 2 show similarity for the first five levels of intermolecular interaction strength. Mechanistically, this work demonstrates the dual catalytic and template roles of Mn(II) in directing both ligand evolution and supramolecular architecture. Overall, this work presents a practical and generalizable strategy for the one-pot synthesis of adaptive coordination materials via metal-mediated heterocycle construction, contributing to ongoing advances in crystal engineering and supramolecular design.
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