title: Tuning Up an Electronic Structure of the Subphthalocyanine Derivatives toward Electron-Transfer Process in Noncovalent Complexes with C60and C70Fullerenes: Experimental and Theoretical Studies.
abstract: Noncovalent π-π interactions between chloroboron subphthalocyanine (1), 2,3-subnaphthalocyanine (3), 1,4,8,11,15,18-(hexathiophenyl)subphthalocyanine (4), or 4-tert-butylphenoxyboron subphthalocyanine (2) with C60and C70fullerenes were studied by UV-vis and steady-state fluorescence spectroscopy, as well as mass (APCI, ESI, and CSI) spectrometry. Mass spectrometry experiments were suggestive of relatively weak interaction energies between compounds 1-4 and fullerenes. The formation of a new weak charge-transfer band in the NIR region was observed in solution only for subphthalocyanine 4 when titrated with C60and C70fullerenes. Molecular structures of the subphthalocyanines 2 and 4 as well as cocrystallite of 4 with C60fullerene (4···C60) were studied using X-ray crystallography. One of the C60fullerenes in the crystal structure of 4···C60was found in the concave region between two subphthalocyanine cores, while the other three fullerenes are aligned above individual isoindole fragments of the aromatic subphthalocyanine. The excited-state dynamics in noncovalent assemblies were studied by transient absorption spectroscopy. The time-resolved photophysics data suggest that only electron-rich subphthalocyanine 4 can facilitate an electron-transfer to C60or C70fullerenes, while no electron-transfer from the photoexcited receptors 1-3 to fullerenes was observed in UV-vis and transient spectroscopy experiments. DFT calculations using the CAM-B3LYP exchange-correlation functional and the 6-31+G(d) basis set allowed an estimation of interaction energies for the noncovalent 1:1 and 1:2 (fullerene:subphthalocyanine) complexes. Theoretical data suggest that the weak (∼3.5-10.5 kcal/mol) van der Waals-type interaction energies tend to increase with an increase of the electron density at the subphthalocyanine core with compound 4 being the best platform for noncovalent interactions with fullerenes. DFT calculations also indicate that 1:2 (fullerene:subphthalocyanine) noncovalent complexes are more stable than the corresponding 1:1 assemblies.
authors.affiliation: Department of Chemistry and Biochemistry, University of Minnesota Duluth , 1039 University Drive, Duluth, Minnesota 55812, United States.
authors.forename: Hannah M
authors.initials: HM
authors.lastname: Rhoda
authors.affiliation: Department of Chemistry and Biochemistry, University of Minnesota Duluth , 1039 University Drive, Duluth, Minnesota 55812, United States.
authors.forename: Mathew P
authors.initials: MP
authors.lastname: Kayser
authors.affiliation: Department of Chemistry, University of Minnesota , 207 Pleasant Street SE, Minneapolis, Minnesota 55455, United States.
authors.forename: Yefeng
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Chemistry Department, State University of New York, College at Buffalo , 1300 Elmwood Avenue, Buffalo, New York 14222, United States.
authors.forename: Alexander Y
authors.initials: AY
authors.lastname: Nazarenko
authors.affiliation: Institute for Materials Research, Tohoku University , Sendai 980-8577, Japan.
authors.forename: Rodion V
authors.initials: RV
authors.lastname: Belosludov
authors.affiliation: Department of Chemistry and Biochemistry, University of Minnesota Duluth , 1039 University Drive, Duluth, Minnesota 55812, United States.
authors.forename: Paul
authors.initials: P
authors.lastname: Kiprof
authors.affiliation: Department of Chemistry, University of Minnesota , 207 Pleasant Street SE, Minneapolis, Minnesota 55455, United States.
authors.forename: David A
authors.initials: DA
authors.lastname: Blank
authors.affiliation: Department of Chemistry and Biochemistry, University of Minnesota Duluth , 1039 University Drive, Duluth, Minnesota 55812, United States.
authors.forename: Victor N
authors.initials: VN
authors.lastname: Nemykin