Efficient Photoinduced Electron Transfer in a Porphyrin Tripod−Fullerene Supramolecular Complex via π−π Interactions in Nonpolar Media

Abstract

A novel porphyrin tripod (TPZn(3)) was synthesized via "click chemistry". Three porphyrin moieties of TPZn(3) are geometrically close and linked by a flexible linker. The electron-transfer oxidation of TPZn(3) results in intramolecular pi-dimer formation between porphyrin moieties as indicated by electrochemical, vis-NIR, and ESR measurements. The cyclic voltammogram of TPZn(3) exhibited stepwise one-electron oxidation processes of three porphyrin moieties in the range from 0.58 to 0.73 V (vs SCE in CH(2)Cl(2)). When TPZn(3) was oxidized by tris(2,2'-bipyridyl)-ruthenium(III) ([Ru(bpy)(3)](3+)), the oxidized species (TPZn(3))(n+) (0 < n </= 3) exhibited a charge resonance band in the NIR region due to the pi-dimer formation between porphyrin moieties. A supramolecular electron donor-acceptor system was also constructed using TPZn(3). The flexible conformation of TPZn(3) makes it possible to capture a fullerene derivative containing a pyridine moiety (PyC(60)) inside the cavity by pi-pi interactions as well as the coordination bond between Zn(2+) and the pyridine moiety. The formation of a 1:1 supramolecular complex of TPZn(3) with PyC(60) (TPZn(3)-PyC(60)) was indicated in the UV-vis and (1)H NMR spectra in nonpolar solvents. The association constant of TPZn(3) with PyC(60) (1.1 x 10(5) M(-1) in toluene) is much larger as compared with those of the corresponding monomer (MPZn) and dimer porphyrin (DPZn(2)). The dynamics of photoinduced electron transfer from the singlet excited state of TPZn(3) to PyC(60) was examined by laser flash photolysis measurements. The efficient intracomplex photoinduced electron transfer in TPZn(3)-PyC(60) occurred in nonpolar solvents, resulting from the pi-pi interactions between the porphyrin and fullerene moieties, together with intramolecular pi-bond formation between the porphyrin radical cation and the neutral porphyrin in TPZn(3)(*+).

Fulleretic Well‐Defined Scaffolds: Donor–Fullerene Alignment Through Metal Coordination and Its Effect on Photophysics

“…It is important to note that ET was described as the most probable pathway in the fullerene-ZnTCPP dyads in nonpolar solvents. [47] At the same time,while FRET could be responsible for observed emission quenching/lifetime decrease in 1,c harge transfer (CT), often observed for fullerene-porphyrin dyads in polar solvents [48] could not be ruled out. Using the locality of the frontier molecular orbitals in 1,w ep erformed calculations of the excitations for the BPCF-ZnTCPP dyad as atruncated model of 1 comprised of one BPCF coordinated to ZnTCPP through its pyridyl arm (Figure 3).…”

Assembly of carbon nanotubes and alkylated fullerenes: nanocarbon hybrid towards photovoltaic applications

“…17 The extraordinary electron acceptor properties have resulted in noteworthy advances in the research areas of light-induced electron transfer and solar energy conversion. [18][19][20][21] Therefore, the hybridization of C 60 with SWCNTs 5,7,[22][23][24][25][26][27] would couple the optical and electronic properties of SWCNTs together with the electron-acceptor feature of C 60 . Covalent modification is one of the strategies for the attachment of C 60 onto sidewall of SWCNT.…”

New Donor-Acceptor Porphyrin-Fullerene Dyades

“…Однако он образует различные по природе диады с молекулами -донорами электронов, таким как тетратиафульвалены, металлоцены, N,N-диметиламинофенил-производные, рутений(II)-трис-бипиридин, порфирины, фталоцианины, являющиеся предметом многочисленных исследований. [2][3][4][5][6][7][8][9][10][11] Значительный интерес представляют порфирин-фуллереновые диады, образованные за счет донорно-акцепторного координационного взаимодействия между электронодонорным атомом заместителя в фуллерене и атомом металла в металлопорфирине. Пиридильные или имидазольные производные пирролидинил- [60] фуллерена имеют дополнительные реакционные центры и могут выступать донорами электронной плотности по отношению к координационно ненасыщенным металлопорфиринам (MP), образуя с ними координационно-связанные диады [12][13][14][15] и молекулярные комплексы более высокого порядка.…”