Development of External Stimuli Responsive-Dynamic Helicity Inversion Systems based on Coordination Chemistry

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(1) The inversion and transfer of chirality information of supramolecular helices are ubiquitous phenomena in nature. We successfully demonstrated dynamic peptide helix inversion of synthetic peptide-metal complex, in which metal center acts as a time-tuning device. The metal complex used is composed of a chiral hexa-coordinated metal center and two achiral penta-peptide chains. The helix inversion of the peptide chains of the ligand can be followed by helicity inversion of the octahedral metal center upon addition of NO_3^- anion stimulus. Since the inversion rate of complex helicity is tuned based on the substitution lability of the metal center, the present metallo-peptide complex offers time-tunable peptide helix inversion which has time scale from milliseconds to hours.(2) Dynamic and consecutive molecular motions including stretching, winding and rotation are observed in nature. We developed chemical device exhibiting dual mode motions based on a chiral Co(II) complex. The ligand … More employed includes 2,5-dimethoxy benzene moieties attaching to the both terminals of helical tetradentate ligand via amide linkages. The acid-base reaction of its metal complex triggered interconversion of coordinating atoms between amide nitrogen atoms and amide oxygen atoms to offer stretching molecular motion. The employed Co(II) complex also showed helicity inverting motions. Then, the present type of kinetically labile Co(II) complex allows dual molecular motion in a highly dynamic fashion, which is required as sophisticated supramolecular switching device.(3) Polymeric membranes containing Zn(II) complexes with chiral tetradentate ligands were prepared for the determination of nitrate anion. The potentiometric selectivity coefficients were evaluated using fixed interference method, and these Zn(II) complexes exhibited better selectivity for nitrate anion with respect to wide variety of inorganic anions. Since the new Zn(II) complex-based sensors were used as indicator electrodes in determination of the nitrate anion in synthetic water samples, they are recognized as selective carriers for nitrate anions. Less