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Heterometallic [MnPtn(L)2n]x+ Macrocycles from Dichloromethane-Derived Bis-2-pyridyl-1,2,3-triazole Ligands

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posted on 18.08.2016, 19:18 by Dan Preston, Robert A. J. Tucker, Anna L. Garden, James D. Crowley
There is continued interest in the assembly of heterometallic metallosupramolecular assemblies due to the potential for new structural types and/or interesting chemical and physical properties. Two novel methylene-linked bis-2-pyridyl-1,2,3-triazole ligands (1a, 1b) were synthesized through CuAAC “click” chemistry between dichloromethane (DCM), sodium azide, and the appropriate ethynylpyridine, giving the shortest possible “regular” bis-pyridyl-1,2,3-triazole. The first example of bis-coordination of two 2-pyridyl-1,2,3-triazoles (Rpytri) around one Pt­(II) center is reported, giving exclusive formation of head-to-tail [Pt­(Rpytri)2]2+ complexes with vacant binding sites suitable for complexation with other metals and the formation of heterometallic assemblies. The concentration-dependent formation of an equilibrium mixture of a heterometallic [Pd2Pt2(L)4]8+ [4 + 4] square and [Pd3Pt3(L)6]12+ [6 + 6] hexagon was observed, and at lower concentrations ([reactants] = 1.5 mM) hexamer formation was negligible. The [Pt­(L)2]2+ building block could also be utilized in the synthesis of a concentration-independent [Cu2Pt2(L)4]6+ metallomacrocyle. These compounds were characterized with 1H, 13C, and 1H DOSY NMR spectroscopies, elemental analysis, mass spectrometry, and in some cases X-ray crystallography.