TY - JOUR
T1 - A cryptand containing three diiminopyridyl units; aromatic-aromatic interaction and the stability of the complexes
AU - Sato, Tadanobu
AU - Sakai, Ken
AU - Tsubomura, Taro
PY - 1996/1/1
Y1 - 1996/1/1
N2 - The solution properties of a hexaimino cryptand containing 2,6-diiminopyridyl units have been investigated by NMR, UV-VIS absorption and luminescence spectroscopy. The difference in the NMR and UV spectra of the Ba2+ complex and the cryptand is attributed to the conformational change of the diiminopyridyl group. The luminescence spectra of the compounds show near-UV bands and unexpected low-energy bands. The former is attributed to the normal π-π* transition, while the origin of the low-energy bands is discussed in terms of inter- and infra-molecular aromaticaromatic interactions. The inter-molecular interaction is important in the free ligand, however, intra-molecular interaction is suggested in the Ba2+ complex. Further, the specific conformational change of the Ba2+ complex in DMSO-acetonitrile solution is investigated by the measurements of the stability constant of the Ba2+ complex in various DMSO concentrations. The large decrease over 4.0 in logK is found only for the Ba1+ complex. The behavior is explained by the factors brought about the nature of DMSO and the interactions among the diiminopyridyl units, DMSO and the Ba2+ ion.
AB - The solution properties of a hexaimino cryptand containing 2,6-diiminopyridyl units have been investigated by NMR, UV-VIS absorption and luminescence spectroscopy. The difference in the NMR and UV spectra of the Ba2+ complex and the cryptand is attributed to the conformational change of the diiminopyridyl group. The luminescence spectra of the compounds show near-UV bands and unexpected low-energy bands. The former is attributed to the normal π-π* transition, while the origin of the low-energy bands is discussed in terms of inter- and infra-molecular aromaticaromatic interactions. The inter-molecular interaction is important in the free ligand, however, intra-molecular interaction is suggested in the Ba2+ complex. Further, the specific conformational change of the Ba2+ complex in DMSO-acetonitrile solution is investigated by the measurements of the stability constant of the Ba2+ complex in various DMSO concentrations. The large decrease over 4.0 in logK is found only for the Ba1+ complex. The behavior is explained by the factors brought about the nature of DMSO and the interactions among the diiminopyridyl units, DMSO and the Ba2+ ion.
UR - http://www.scopus.com/inward/record.url?scp=0001480799&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0001480799&partnerID=8YFLogxK
U2 - 10.1080/10610279608035192
DO - 10.1080/10610279608035192
M3 - Article
AN - SCOPUS:0001480799
VL - 7
SP - 157
EP - 165
JO - Supramolecular Chemistry
JF - Supramolecular Chemistry
SN - 1061-0278
IS - 2
ER -