TY - JOUR
T1 - Rigid molecular rods with cumulene-bridged polyphosphines
T2 - synthesis, electronic communication, molecular photophysics, mixed-valence state, and X-ray photoelectron spectroscopic study
AU - Ortega, Jeffrey V.
AU - Hong, Bo
AU - Ghosal, Sutapa
AU - Hemminger, John C.
AU - Breedlove, Brian
AU - Kubiak, Clifford P.
PY - 1999
Y1 - 1999
N2 - The synthesis, molecular photophysics, redox characteristics, and electronic interactions, as well as an X-ray photoelectron spectroscopic (XPS) study of a series of Ru(II) and Os(II) complexes with a polyphosphine/cumulene spacer, namely, 1,1′,4,4′-tetrakis(diphenylphosphino)cumulene (C4P4), are studied and compared with the corresponding systems containing spacers with shorter sp carbon chain (Cn lengths. Characterizations of all mono-, homo-, and heterobimetallic complexes with PF6- counteranions are accomplished using 1H, 13C, and 31P{1H} NMR, fast atom bombardment (FAB/MS), and matrix-assisted laser desorption ionization time-of-fiight (MALDI-TOF/MS) mass spectroscopy and elemental analysis. From the electrochemical study it is observed that the length of the Cn bridges has a profound influence on redox potentials and the electronic interaction between the two metal-based termini. XPS studies reveal that a simple change in carbon chain length affects the electron donation of the phosphine spacer to the metal-based termini. As a result, the redox potential of the Ru(II) or Os(II) center is shifted significantly. The comproportionation constant, Kc, is calculated as 1.3 × 107 (M = RuII) or 4.5 × 1010 (M = OsII) for homobimetallic [(bpy)2M(C4P4)M(bpy)2]4+, suggesting a strong electronic communication across the C4P4 spacer. However, the Kc value is estimated to be ca. 4 for the corresponding complexes [(bpy)2M-(C3P4)M(bpy)2]4+ (M = Ru, Os; C3P4 = 1,1′,3,3′-tetrakis(diphenylphosphino)allene), indicative of a system with electronic isolation between the two termini. In heterobimetallic [(bpy)2Ru(CnP4)Os(bpy)2] 4+ (n = 3, 4), the energy transfer from Ru(II) to Os(II) is found to be very efficient, with rate constants kcn of ca. 3 × 109 s-1 (n = 3) and 1 × 1011 s-1 (n = 4). The increased value of ken upon the change from C3 to C4 can be explained by the increase in the electronic communication across spacers. Detailed studies and calculations have revealed a Dexter-type of mechanism for the triplet energy transfer in the system.
AB - The synthesis, molecular photophysics, redox characteristics, and electronic interactions, as well as an X-ray photoelectron spectroscopic (XPS) study of a series of Ru(II) and Os(II) complexes with a polyphosphine/cumulene spacer, namely, 1,1′,4,4′-tetrakis(diphenylphosphino)cumulene (C4P4), are studied and compared with the corresponding systems containing spacers with shorter sp carbon chain (Cn lengths. Characterizations of all mono-, homo-, and heterobimetallic complexes with PF6- counteranions are accomplished using 1H, 13C, and 31P{1H} NMR, fast atom bombardment (FAB/MS), and matrix-assisted laser desorption ionization time-of-fiight (MALDI-TOF/MS) mass spectroscopy and elemental analysis. From the electrochemical study it is observed that the length of the Cn bridges has a profound influence on redox potentials and the electronic interaction between the two metal-based termini. XPS studies reveal that a simple change in carbon chain length affects the electron donation of the phosphine spacer to the metal-based termini. As a result, the redox potential of the Ru(II) or Os(II) center is shifted significantly. The comproportionation constant, Kc, is calculated as 1.3 × 107 (M = RuII) or 4.5 × 1010 (M = OsII) for homobimetallic [(bpy)2M(C4P4)M(bpy)2]4+, suggesting a strong electronic communication across the C4P4 spacer. However, the Kc value is estimated to be ca. 4 for the corresponding complexes [(bpy)2M-(C3P4)M(bpy)2]4+ (M = Ru, Os; C3P4 = 1,1′,3,3′-tetrakis(diphenylphosphino)allene), indicative of a system with electronic isolation between the two termini. In heterobimetallic [(bpy)2Ru(CnP4)Os(bpy)2] 4+ (n = 3, 4), the energy transfer from Ru(II) to Os(II) is found to be very efficient, with rate constants kcn of ca. 3 × 109 s-1 (n = 3) and 1 × 1011 s-1 (n = 4). The increased value of ken upon the change from C3 to C4 can be explained by the increase in the electronic communication across spacers. Detailed studies and calculations have revealed a Dexter-type of mechanism for the triplet energy transfer in the system.
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U2 - 10.1021/ic990673m
DO - 10.1021/ic990673m
M3 - Article
AN - SCOPUS:0000725039
SN - 0020-1669
VL - 38
SP - 5102
EP - 5112
JO - Inorganic Chemistry
JF - Inorganic Chemistry
IS - 22
ER -