The IR and U V absorption spectra as well as the Raman spectra of monomer and dimer of 2-pyridone were studied. The molecular weight of 2-pyridone in benzene and dimethyl sulfoxide was determined in order to examine the association. 2-Pyridone in nonpolar solvents shows two types of carbonyl stretching vibration bands due to the coexistence of the monomer and dimer. The highest wavelength UV absorption of 2-pyridone in isooctane (2,2,4-trimethylpentane) is ascribed to π-π* electronic transitions of the monomer and dimer. The dimer absorption band appears at a higher wavenumber than that of the monomer by ca. 830 cm−1. The dimer band corresponds to the π-π* transition from the ground 1Ag state to the excited 1Bu state. No π-π* transition absorption from the ground 1Ag state to the excited 1Ag state could be observed because of the g-g Laporte forbiddance in the transition under an assumption of the molecular C2h symmetry.
Through-space interactions in non-Kekulé biradicals were analyzed. We defined PNBMOi,j as a product of i-th and j-th NBMO of non-Kekulé biradicals. Whereas through-space interactions between non-nearest-neighbor carbon atomic sites in PNBMOi,j were negligible in so-called disjoint-type biradicals, antibonding-through-space interactions between second-nearest-neighbor carbon atomic sites in PNBMOi,j destabilized the singlet states in so-called nondisjoint-type biradicals. The instabilities in the singlet states contributed to the triplet state preference for nondisjoint-type biradicals.
The substituent effects on the metal-ion-capturing function of amidinourea resins were investigated. The metal-ion-capturing function likely depends on the steric effects and/or hydrophilic/hydrophobic properties of the three substituents around the capturing sites. In order to clarify these points, we synthesized eight amidinourea resins having acyclic-and cyclic substituents with various numbers of carbon atoms. The adsorption analysis and the water-solubility test indicated that the hydrophilic/hydrophobic properties are more important for the metal-ion-capturing function than the steric effects. From the results including those with the unsubstituted amidinourea resin, we concluded that the optimized structure for metal-ion-capturing amidinourea resins is one with three methyl substituents.
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