Conformation Locking of the Pentose Ring in Nucleotide Monophosphate Coordination Polymers via π–π Stacking and Metal-Ion Coordination
The conformation of the pentose ring in nucleotides is extremely important and a basic problem in biochemistry and pharmaceutical chemistry. In this study, we used a strategy to regulate the conformation of pentose rings of nucleotides via the synergistic effect of metal-ion coordination and π–π stacking. Seven types of coordination complexes were developed and characterized using Fourier transform infrared spectroscopy, elemental analysis, thermogravimetric analysis, powder X-ray diffraction, ultraviolet–visible spectroscopy, 1H nuclear magnetic resonance spectroscopy, electrospray ionization mass spectrometry, and single-crystal X-ray diffraction. On the basis of two conformational parameters obtained from single-crystal structure analysis, i.e., the pseudorotation phase angle and degree of puckering, the exact conformation of the furanose ring in these coordination polymers was unequivocally determined. Crystallographic studies demonstrate that a short bridging ligand (4,4′-bipyridine) is conducive to the formation of a twist form, and long auxiliary ligands [1,2-bis(4-pyridyl)ethene and 4,4′-azopyridine] induce the formation of an envelope conformation. However, the longest auxiliary ligands [1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene] cannot limit the flexibility of a nucleotide. Our results demonstrated that the proposed strategy is universal and controllable. Moreover, the chirality of these coordination polymers was examined by combining the explanation of their crystal structures with solid-state circular dichroism spectroscopy measurements.
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