Naphthalene monoimide

The complex in Figure 11.18 successfully induces photoinduced proton reduction, hut with very low activities. Provide two reasons why using naphthalene monoimide dithiolates as the linker between the photosensitizer and the active site for proton reduction was considered desirable. What spectral argument was used to reason that the ground state zinc porphyrin moiety does not interact electronically with the diiron portion of this complex ... 

Several methods have been reported for the monofunctionaUzation of PDI [6] including one-pot imidization (route A) or a base-promoted coupling reaction between naphthalene monoimide derivatives (route B) [7], as shown in Scheme 2. We found the one-pot imidizatitMi reaction (route A) to be more practical than route B route B consisted of five steps and the open-form product 6b was labile under the basic reaction conditions required to produce the closed product 6a. The one-pot imidization, route A, was simple and 3 could easily be recovered via column chromatography because the use of an excess amount of 3 was necessary. Concerning the solubility and reactivity of perylene tetracarboxylic acid dianhydride (PDA) 4, the imidization of 4 was, first, carried out with 2,6-ditsopropylaniline (5) in imidazole then 3 in propionic acid solution was added to produce the closed product PDI 6a. 

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. 

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. 

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