Elongation of lifetime of the charge-separated state of ferrocene-naphthalenediimide-[60]fullerene triad via stepwise electron transfer.

Supur, Mustafa,El-Khouly, Mohamed E,Seok, Jai Han,Kay, Kwang-Yol,Fukuzumi, Shunichi American Chemical Society 2011 The journal of physical chemistry. A, Molecules, s Vol.115 No.50

<P>Photoinduced electron-transfer processes of a newly synthesized rodlike covalently linked ferrocene-naphthalenediimide-[60]fullerene (Fc-NDI-C(60)) triad in which Fc is an electron donor and NDI and C(60) are electron acceptors with similar first one-electron reduction potentials have been studied in benzonitrile. In the examined Fc-NDI-C(60) triad, NDI with high molar absorptivity is considered to be the chromophore unit for photoexcitation. Although the free-energy calculations verify that photoinduced charge-separation processes via singlet- and triplet-excited states of NDI are feasible, transient absorption spectra observed upon femtosecond laser excitation of NDI at 390 nm revealed fast and efficient electron transfer from Fc to the singlet-excited state of NDI ((1)NDI*) to produce Fc(+)-NDI(?-)-C(60). Interestingly, this initial charge-separated state is followed by a stepwise electron transfer yielding Fc(+)-NDI-C(60)(?-). As a result of this sequential electron-transfer process, the lifetime of the charge-separated state (τ(CS)) is elongated to 935 ps, while Fc(+)-NDI(?-) has a lifetime of only 11 ps.</P>

Enhancement of Photodriven Charge Separation by Conformational and Intermolecular Adaptations of an Anthracene–Perylenediimide–Anthracene Triad to an Aqueous Environment

Supur, Mustafa,Sung, Young Mo,Kim, Dongho,Fukuzumi, Shunichi American Chemical Society 2013 JOURNAL OF PHYSICAL CHEMISTRY C - Vol.117 No.24

<P>Photoinduced electron-transfer dynamics of an electron donor–acceptor–donor triad, consisting of anthracenes and perylenediimide (An<SUB>2</SUB>PDI), were investigated in different media by using time-resolved laser spectroscopic techniques. The aromatic components are attached by flexible linkers containing hydrophilic quaternary ammonium joints in the triad. In MeOH, in which An<SUB>2</SUB>PDI dissolves completely, no electron-transfer products were observed in the transient absorption measurements after the excitation of anthracenes and PDI because of the rapid back-electron transfer. The charge-separation rate of the triad in MeOH was estimated as 1.2 × 10<SUP>10</SUP> s<SUP>–1</SUP> from the quenching of the singlet-excited state of PDI. In contrast, the formation of electron-transfer products was evident in water, and the electron-transfer rate was 200 times faster than the rate in MeOH in the course of the excitations of the selected components of An<SUB>2</SUB>PDI (2.5 × 10<SUP>12</SUP> s<SUP>–1</SUP>). It is concluded from the time-resolved data that the conformational disposition of the hydrophilic joints due to hydrophilic–lipophilic interactions and the facile π-stacking of hydrophobic PDI cores in water results in the contraction and the relative rigidity of the electron-transfer distance and the intermolecular stabilization of electron-transfer species within the polymeric self-assemblies of An<SUB>2</SUB>PDI, enabling an efficient photodriven electron-transfer process to occur.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2013/jpccck.2013.117.issue-24/jp403285k/production/images/medium/jp-2013-03285k_0010.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp403285k'>ACS Electronic Supporting Info</A></P>

Tuning the photodriven electron transport within the columnar perylenediimide stacks by changing the π-extent of the electron donors

Supur, Mustafa,Fukuzumi, Shunichi The Royal Society of Chemistry 2013 Physical chemistry chemical physics Vol.15 No.7

<P>Photodriven electron-transport properties of the self-assemblies of <I>N</I>,<I>N</I>′-di(2-(trimethylammoniumiodide)ethylene)perylenediimide stacks (TAIPDI)<SUB><I>n</I></SUB> with three electron donors, disodium 4,4′-bis(2-sulfonatostyryl)biphenyl (BSSBP, stilbene-420), sodium 9,10-dimethoxyanthracene-2-sulfonate (DANS) and disodium 6-amino-1,3-naphthalenedisulfonate (ANADS) have been studied in water. These electron donors vary in their π-extent to adjust the electronic coupling and the distance with the PDI stacks. Possessing the largest π-extent, BSSBP has strong π–π interactions as well as ionic interactions with (TAIPDI)<SUB><I>n</I></SUB>. Instead of π-stacking with TAIPDI planes, DANS and ANADS, with a relatively small π-extent, are embedded in the side chains of TAIPDIs <I>via</I> ionic interactions, resulting in a distance increment from the aromatic TAIPDI cores. After excitation, the BSSBP–(TAIPDI)<SUB><I>n</I></SUB> system exhibits fast charge separation (0.70 ps) and relatively slow charge recombination (485 ps) due to intermolecular electron delocalization along the TAIPDI stacks. On the other hand, charge separation in DANS–(TAIPDI)<SUB><I>n</I></SUB> and ANADS–(TAIPDI)<SUB><I>n</I></SUB> occurs within 1.5 and 1.6 ns, respectively, calculated from the quenching of singlet excited states. The lifetimes of charge-separated states are determined to be 44 and 96 μs, at least 10<SUP>5</SUP> times slower than that of BSSBP–(TAIPDI)<SUB><I>n</I></SUB> due to remarkably improved electron transport throughout the (TAIPDI)<SUB><I>n</I></SUB>.</P> <P>Graphic Abstract</P><P>Electron transport within the columnar perylenediimide stacks is regulated by changing the distance, with electron donors having different π-extents. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2cp44106c'> </P>

Excitation energy transfer from non-aggregated molecules to perylenediimide nanoribbons <i>via</i> ionic interactions in water

Supur, Mustafa,Yamada, Yusuke,Fukuzumi, Shunichi The Royal Society of Chemistry 2012 Journal of materials chemistry Vol.22 No.25

<P>Two energy donor–acceptor self-assembly systems have been constructed by using π–π, lipophilic, and ionic interactions in water. π-stacked <I>N</I>,<I>N</I>′-ditridecylperylenediimide (PDI), which forms nanoribbons, has been dispersed in water in the presence of myristyltrimethylammonium bromide (MTAB) through lipophilic interactions of tridecyl groups of PDIs with long tails of MTAB molecules. Cationic heads of MTAB molecules, anchored on the bulk of the side-chains of the nanoribbons, attract water-soluble zinc tetra(4-sulfonatophenyl)porphyrin tetrapotassium salt (ZnTPPSK<SUB>4</SUB>) and lucifer yellow CH dipotassium salt (LY). By this design, efficient photosensitization of non-aggregated energy donors, ZnTPPSK<SUB>4</SUB> and LY, has been achieved while retaining the one-dimensional order at nanoscale, resulting in the efficient excitation energy transfer to PDI nanoribbons in each system.</P> <P>Graphic Abstract</P><P>Energy transfer to PDI nanoribbons was achieved in two supramolecular systems constructed by π–π, lipophilic, and ionic interactions in water. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2jm31661g'> </P>

Photodriven Electron Transport within the Columnar Perylenediimide Nanostructures Self-Assembled with Sulfonated Porphyrins in Water

Supur, Mustafa,Fukuzumi, Shunichi American Chemical Society 2012 The Journal of Physical Chemistry Part C Vol.116 No.44

<P>Columnar stacks of <I>N</I>,<I>N</I>′-di(2-(trimethylammoniumiodide)ethylene) perylenediimide (TAIPDI)<SUB><I>n</I></SUB> can host <I>meso</I>-tetrakis(4-sulfonatophenyl)porphyrin zinc tetrapotassium salt (ZnTPPSK<SUB>4</SUB>) molecules at different ratios through the ionic and π–π interactions prompted by an aqueous environment. Photoexcitation of this host–guest complex generates very fast charge separation (1.4 × 10<SUP>12</SUP> s<SUP>–1</SUP>). Charge recombination is markedly decelerated by a probable electron delocalization mechanism along the long-range of tightly stacked TAIPDIs (4.6 × 10<SUP>8</SUP> s<SUP>–1</SUP>), giving an exceptional <I>k</I><SUB>CS</SUB>/<I>k</I><SUB>CR</SUB> ratio of 3000 as determined by using time-resolved transient absorption techniques.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2012/jpccck.2012.116.issue-44/jp308549w/production/images/medium/jp-2012-08549w_0013.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp308549w'>ACS Electronic Supporting Info</A></P>

Electron Delocalization in One-Dimensional Perylenediimide Nanobelts through Photoinduced Electron Transfer

Supur, Mustafa,Yamada, Yusuke,El-Khouly, Mohamed E.,Honda, Tatsuhiko,Fukuzumi, Shunichi American Chemical Society 2011 JOURNAL OF PHYSICAL CHEMISTRY C - Vol.115 No.30

<P>Photoinduced electron transfer (PET) of a hybrid system comprising <I>N</I>,<I>N</I>′-ditridecylperylenediimide (LPDI), which forms nanobelt structures of the form (LPDI)<SUB><I>n</I></SUB>, and soluble zinc (tetra-<I>tert</I>-butyl)phthalocyanine (ZnTBPc) has been investigated in polar benzonitrile. The PET of a mixture system comprising <I>N</I>,<I>N</I>′-diheptadecan-9-ylperylene- diimide (BPDI) dissolved thoroughly in benzonitrile and ZnTBPc was also examined for comparison. LPDI nanobelt structures were identified using steady-state absorption and emission spectroscopies, as well as dynamic light scattering (DLS), in suspension and detected using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) in the solid state. The electron paramagnetic resonance (EPR) spectrum of the radical anion of LPDI nanobelts [(LPDI)<SUB><I>n</I></SUB><SUP>•–</SUP>] was quite different from that of BPDI (BPDI<SUP>•–</SUP>) because of enhanced electron delocalization within the one-dimensional LPDI aggregates. Polar benzonitrile enables intermolecular light-induced electron transfer from the low-lying triplet state of ZnTBPc to the LPDI nanobelts through its stabilization effect on the electron-transfer species, as indicated by free energy calculations. Nanosecond transient absorption spectra displayed marked broadening of the radical anion peak of LPDI nanobelts in the near-infrared (NIR) region upon excitation, confirming the delocalization of the transferred electron within the nanostructure. Whereas both the hybrid and mixture systems have nearly the same rate constants (<I>k</I><SUB>et</SUB>) of PET from the PDIs to ZnTBPc, the rate of back electron transfer (<I>k</I><SUB>bet</SUB>) of (LPDI)<SUB><I>n</I></SUB><SUP>•–</SUP>/ZnTBPc<SUP>•+</SUP> is lower than that of BPDI<SUP>•–</SUP>/ZnTBPc<SUP>•+</SUP>, which might result from the effect of electron delocalization within the nanobelt structure.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2011/jpccck.2011.115.issue-30/jp204417v/production/images/medium/jp-2011-04417v_0014.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp204417v'>ACS Electronic Supporting Info</A></P>