TY - JOUR
T1 - Solvent effect in randomly and partially oriented triplets of the sapphyrin dication. Optical and fast EPR-magnetophotoselection measurements
AU - Regev, Ayelet
AU - Michaeli, Shalom
AU - Levanon, Haim
AU - Cyr, Mike
AU - Sessler, Jonathan L.
PY - 1991/1/1
Y1 - 1991/1/1
N2 - The photoexcited triplet state of the sapphyrin dication, H5·SaP2+, was investigated by optical absorption and fast EPR-magnetophotoselection (MPS) spectroscopies. Results indicate that H5·SaP2+ exists as a monomer in nonpolar isotropic solvents (chloroform and toluene) and nematic liquid crystals, while in a polar solvent, e.g., ethanol, the stable form exists as a face-to-face dimer via specific solvent-mediated interactions. Analysis of the MPS-triplet EPR and optical absorption results provides the following conclusions: (i) relation between the molecular and magnetic frames of references; (ii) out-of-plane location of the optical transition moment for both the monomer, (H5·Sap2+, and the dimer, (H5·Sap2+)2, suggesting a possible admixture of (n,π*) and (π,π*) states; (iii) in-plane triplet spin alignment and planar molecular structure of the monomer; (iv) a negative value of the zero-field splitting parameter, D, for the monomer and the dimer.
AB - The photoexcited triplet state of the sapphyrin dication, H5·SaP2+, was investigated by optical absorption and fast EPR-magnetophotoselection (MPS) spectroscopies. Results indicate that H5·SaP2+ exists as a monomer in nonpolar isotropic solvents (chloroform and toluene) and nematic liquid crystals, while in a polar solvent, e.g., ethanol, the stable form exists as a face-to-face dimer via specific solvent-mediated interactions. Analysis of the MPS-triplet EPR and optical absorption results provides the following conclusions: (i) relation between the molecular and magnetic frames of references; (ii) out-of-plane location of the optical transition moment for both the monomer, (H5·Sap2+, and the dimer, (H5·Sap2+)2, suggesting a possible admixture of (n,π*) and (π,π*) states; (iii) in-plane triplet spin alignment and planar molecular structure of the monomer; (iv) a negative value of the zero-field splitting parameter, D, for the monomer and the dimer.
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U2 - 10.1021/j100176a019
DO - 10.1021/j100176a019
M3 - Article
AN - SCOPUS:0040180890
SN - 0022-3654
VL - 95
SP - 9121
EP - 9129
JO - Journal of Physical Chemistry
JF - Journal of Physical Chemistry
IS - 23
ER -