Porphyrin triads

Figure 59 (Top) Steady-state emission spectra (Xexc = 450 nm) of adsorbed monolayers of Coum-PAH and Fl-PAH polycations, PdTAPP+, and the coadsorbed coumarin-flu-orescein-porphyrin triad. (Bottom) Emission spectra of a similar triad containing PdT-SPP4, with and without an added viologen electron acceptor layer. (From Ref. 43a. Copyright 1999 Elsevier Publications.)...

Photoinduced intramolecular electron transfer in porphyrin triads of 4he type [zinc octaethylporphyrin-4,4 -bipyridinium-tetraphenylporphyrin] occurs either from the singlet state of the zinc porphyrin ( A) or from the corresponding free base ( B) with formation of or An... 

Self-assembly principles of the formation of multiporphyrin arrays are extended to anchor the porphyrin triads on semiconductor CdSe/ZnS quantum dot (QD) surface. Comparing with individual counterparts (QD, pyridylsubstituted porphyrin H2P(p-Pyr)4, and Zn-octaethylporphyrin chemical dimer (ZnOEP Ph), the formation of heterocomposites QD-porphyrin triad results in the specific quenching of QD photoluminescence, accompanied by the dimer fluorescence strong quenching (Tsd 1-7 ps due to energy and/or electron transfer) and the noticeable decease of the extra-ligand H2P(p-Pyr)4 fluorescence efficiency by 1.5-2 times via hole transfer H2P—>dimer. 

Typically, for porphyrin triads (ZnOEP)2Ph H2P(p-Pyr)2 the deactivation pathways may be presented as follows [5]. The dimer fluorescence shows the strong quenching (fluorescence decay is shorten from tSd°= 115 ns down to TSD 1.7ps in toluene at 295 K) caused by both S-S energy transfer (rate constant k5= 6.7xlOlo-7.5xlO10 s 1, Fig. 1) and the photoinduced electron transfer (rate constant k() > 8x IO10 s"1). Fluorescence spectra of the triads mainly... 

Fig.31 Structures of the a a Zn-porphyrin-Ceo-free base-porphyrin triad (39) [18,20,24], and b a BDP-Zn-porphyrin-free base porphyrin triad (40) [99]...

Table 2. Absorption and emission properties of bis(thienylalko y)-and bis(oligothienylalkoxy)-phosphorus(V)porphyrin triad molecules in CH3CN...

Figure 13.32. Porphyrin triads with MgP, ZnP, and H2P components. The linking position of the MgP has been systematically varied using a p-phenyl spacer at the meso position in 39, and at a beta position in 40. In 41 and 42, m-phenyl spacers are attached at meso and beta carbons, respectively.

Figure 13.62. Rotaxane porphyrin triads built around a bis(phenanthroline) complex.

A series of porphyrin trimers linked into a star-shaped constract with triary-lamine in the center was synthesized and applied to BHJ SCs [125-127]. These porphyrins were used as either donors or acceptors in the BHJ SCs. The PCE of these BHJ SCs was higher if these porphyrins served as D components of the active material. The PCE of these cells did not exceed 0.4 % [125, 126]. Recently, a similar triazine-bridged ZnP triad approached PCE of 4 % (Table 27, Scheme 56) [127]. Apparentiy, this improvement was due to symmetry breaking in the porphyrin triad. That is, two ZnPs with phenyl i 5o-substituents were linked with free-base porphyrin bearing one carboxyphenyl and two 2,4,6-trimethylphenyl substituents. 

Sharma GD, Zervaki GE, Angaridis PA et al (2014) Triazine-bridged porphyrin triad as electron donor for solution-processed bulk hetero-junction organic solar cells. J Phys Chem C 118(ll) 5968-5977... 

The porphyrin-TTF series was extended and the behavior of symmetric and asymmetric donor-acceptor systems evaluated. Novel symmetric porphyrin-te-trathiafulvalene-porphyrin triads annulated through quinoxaline linkers into planar and extended ji-conjugated molecules were synthesized and its behavior compared with porphyrin-tetrathiafulvalene dyads [231]. Cyclic voltammetry and spectro-electrochemical methods were utilized to elucidate the redox processes of both compounds. The first oxidation of the triad in the peripheral porphyrin sites was followed by the formation of TTF radicals, but this sequence was reversed in the corresponding dyad. Ab initio calculations were realized demonstrating that TTF-type and porphyrin-type HOMOs have similar energies thus explaining that behavior. 

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