Electron naphthalene diimide

Near-infrared (NIR) absorption spectroscopy has been used to characterize the delocalized re-stacks on electronic conducting dendrimers by Miller and coworkers [47-49]. These dendrimers were prepared by peripherally modifying PAMAM dendrimers with cationically substituted naphthalene diimides, and then reduced with one electron per imide group to convert each imide into its anion radical. The re-stacking of these radical anions on these dendrimer surfaces was indicated by an absorbance band beyond 2000 nm in the NIR spectra. 

Quite differently, Pleux et al. tested a series of three different organic dyads comprising a perylene monoimide (PMI) dye linked to a naphthalene diimide (NDI) or C60 for application in NiO-based DSSCs (Fig. 18.7) [117]. They corroborated a cascade electron flow from the valance band of NiO to PMI and, finally, to C60. Transient absorption measurements in the nanosecond time regime revealed that the presence of C60 extends the charge-separated state lifetime compared to just PMI. This fact enhanced the device efficiencies up to values of 0.04 and 0.06% when CoII/m and P/Ij electrolytes were utilized, respectively. More striking than the efficiencies is the remarkable incident photon-to-current efficiency spectrum, which features values of around 57% associated to photocurrent densities of 1.88 mA/cm2. 

An example of the difficulties encountered when trying to fabricate an ohmic electrode, able to sustain a space-charge-limited current, is the recent work of the Neher group [179]. The authors deposited barium as an electron injection cathode on top of an electron transporting polymer based on a naphthalene diimide core whose LUMO is as low as 4 eV below vacuum level. Although the Fermi level of barium should be above the LUMO of the polymer, the electron current is. 

Other electroactive groups incorporated in gold-thiol monolayers include tetrathiaful-valene365 and fullerene393. Miller and coworkers prepared thiol-derivatized oligoimides with naphthalene diimide electroactive groups. Electron transfer to each electroactive function was observed394,395. 

Mechanically responsive n-n interactions have also been utilized in supramo-lecular polymers, where n-n stacking between electronically complementary (i.e., electron-rich and electron-poor) n-conjugated groups has been utilized to achieve supramolecular polymerization [57-60]. For example, pairs of naphthalene diimide groups that were introduced into the backbone and termini of polymer PI (Fig. 13) bind to pyrene moieties that were introduced to both ends of polymer P2. 

Sessler. J.L. Brown, C.T. O Connor, D. Springs. S.L. Wang. R. Sathiosatham, M. Hirose, T. A rigid chlorin-naphthalene diimide conjugate. A possible new noncova-lent electron transfer model system. J. Org. Chem. 1998. 63 (21). 7370-7374. 

Flamigni, L. and M.R. Johnston (2001). Photoinduced electron transfer in a non-covalently linked donor-acceptor system A bis-porph5rinic host and a naphthalene diimide guest. Afew. J. Chem. 25(11), 1368-1370. 

Table 14.1 presents a selection of donor/acceptor combinations that have shown notable solar cell efficiencies. Power conversion efficiencies of 1.5-2.2% have been demonstrated for a number of systems, with most blends utilizing either a CN-PPV derivative or the fluorene-dithienylbenzothiadiazole copolymer F8TBT as the acceptor. Despite their high electron mobilities, perylene diimide- and naphthalene diimide-based acceptors have shown disappointing efficiencies, though with optimization Zhou et al. have recently been able to achieve a power conversion efficiency of 2.2% with a perylene diimide acceptor [25]. 

G = 3 PAMAM dendrimers surface modified with cationically substituted naphthalene diimides (Figure 44(a) and (b)). In all cases, the eonductivity was electronic and isotropic. Near infrared spectra showed the formation of extensive tt-stacking, which presumably favored electron hopping via a three-dimensional network. 

Sazanovich IV, Alamiry MAH, Best J et al (2008) Excited state dynamics of a Pt(II) diimine complex bearing a naphthalene-diimide electron acceptor. Inorg Chem 47 10432-10445... 

They are formed by (a) a desymmetrized electron acceptor ring containing two different units, namely a 4,4 -bipyridinium dication (BPY " and a neutral naphthalene diimide (NDI) or pyromellitic diimide (PMI) moiety, and (b) an electron donor ring that can be symmetric for the presenee of two identical dioxybenzene (DOB) or dioxynaphthalene (DON) units, or desymmetrized by the presence of two different donors, i.e. a tetrathiafulvalene (TTF) and a DON moiety. 

Takenaka S, Uto Y, Takagi M, Kondo H (2005) Enhanced electron transfer from glucose oxidase to DNA-immobilized electrode aided by ferrocenyl naphthalene diimide, a threading interealator. Chem Lett 27 989-990... 

While such a device has yet to be constructed, Debreczeny and co-workers have synthesized and studied a linear D-A, -A2 triad suitable for implementation in such a device.11641 In this system, compound 6, a 4-aminonaphthalene monoimide (AN I) electron donor is excited selectively with 400 nm laser pulses. Electron transfer from the excited state of ANI to Ai, naphthalene-1,8 4,5-diimide (NI), occurs across a 2,5-dimethylphenyl bridge with x = 420 ps and a quantum yield of 0.95. The dynamics of charge separation and recombination in these systems have been well characterized.11651 Spontaneous charge shift to A2, pyromellitimide (PI), is thermodynamically uphill and does not occur. The mechanism for switching makes use of the large absorption cross-section of the NI- anion radical at 480 nm, (e = 28,300). A second laser pulse at 480 nm can selectively excite this chromophore and provide the necessary energy to move the electron from NI- to PI. These systems do not rely on electrochemical oxidation-reduction reactions at an electrode. Thus, switching occurs on a subpicosecond time scale. 

The transient Q-band EPR experiments provide direct evidence for sequential electron transfer from the primary to the secondary radical pair of the triplet channel in a triad consisting of a zinc-9-desoxo-meso-methylpyrochlorophyllide donor (ZC), a pyromellitimide primary acceptor (PI), and a naphthalene-1,8 4,5-diimide secondary acceptor oriented in a liquid crystal (Heinen et al., 2002). At room temperature this process occurs with an exponential time constant of tT = 50 + 1 ns. In the singlet-initiated channel, the intramolecular electron-transfer rates are too fast for direct EPR detection. The species decay with a time constant of tS = 36 1 ns by charge recombination to the singlet ground state. 

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