Photochemical Charge Separation in Supramolecular Phthalocyanine−Multifullerene Conjugates Assembled by Crown Ether-Alkyl Ammonium Cation Interactions

Unexpected Supramolecular-Induced Redox Switching in Sandwich Gd Bisphthalocyaninate

The redox state of the phthalocyanine in sandwich lanthanide complexes is crucial for their applications. In this work, we demonstrate that the cation-induced supramolecular assembly of crown-substituted phthalocyanine lanthanide complexes Ln[(15C5)4Pc]2 can be used to control the redox state of the ligand simultaneously with the coordination sphere of the central metal. We achieve unprecedented redox switching of phthalocyanine ligands in a double-decker Gd(III) complex, resulting from the intramolecular inclusion of potassium cations between the decks with simultaneous twisting of the ligands (the skew angle between them decreases from 44.61 to 0.21°). Such a structural change leads to an increase in the deck-to-deck distance and drastically facilitates ligand reduction. This process was shown to be anion-dependent: only potassium salts of weak acids (KOPiv and KOAc) induce intramolecular inclusion of cations with redox switching in contrast to salts of strong acids (KBr, KOPic, KSCN, and KPF6), where such a redox process does not occur. This breakthrough opens new avenues for controlling the electrochromic properties, of phthalocyanines, along with other properties, such as electrical conductivity, optics, etc.

Femtosecond excited state dynamics of stilbene-viologen complexes with a weakly pronounced charge transfer

The femtosecond dynamics of photoinduced electron transfers in supramolecular donor-acceptor complexes between (E)-bis(18-crown-6)stilbene (D) and tetraperchlorates of 2,7-di(2-ammonioethyl)(2,7-diazapyrenium) (A1), 3,3'-(E)-ethene-1,2-diylbis[1-(3-ammoniopropyl)pyridinium] (A2) and 4,4'-ethane-1,2-diylbis[1-(3-ammoniopropyl)pyridinium] (A3) was studied. The acceptors A2 and A3 are weak electron acceptors whose first reduction potentials are equal to -1.0 and -1.2 V (Ag), respectively, while A1 is a strong acceptor with a reduction potential of -0.42 V. It was shown that the back electron transfer time in CT-states of the complexes D·A2 and D·A3 is 30-40 ps, which is approximately 50 times greater than the analogous time for the charge transfer complexes studied earlier. The complex D·A1 is characterized by ultrafast back electron transfer (770 fs). The relaxation pathway of excited states of D·A1 depends on the wavelength of the excitation light. When excited at 356 nm, the accumulation of a transient locally excited (LE) state with a 250 fs lifetime was observed. But when excited at 425 nm, the formation of the LE-state was not observed.

[60]Fullerene–porphyrin [n]pseudorotaxanes: self-assembly, photophysics and third-order NLO response

Herein we report a series of porphyrin and methano[60]fullerene that undergo self-assembly.

Dicyanobenzene and dicyanopyrazine derived X-shaped charge-transfer chromophores: comparative and structure-property relationship study

A series of novel X-shaped push-pull compounds based on benzene-1,2-dicarbonitrile has been designed, synthesized and further investigated by X-ray analysis, electrochemistry, absorption and emission spectra, SHG experiment and quantum-chemical calculations. The obtained data were compared with those for isolobal 5,6-disubstituted pyrazine-2,3-dicarbonitriles. Structure-property relationships were elucidated. The extension, composition and planarization of the π-linker used as well as the electron-withdrawing ability of both dicyano-substituted acceptor units affect the linear and nonlinear properties of the target charge-transfer chromophores most significantly.

Monoisomeric phthalocyanine-fullerene dyads with e- and cis-3 addition pattern; synthesis, modeling, photovoltage and solar cell experiments

Synthesis and characterization of two A 2 B 2-type monoisomeric phthalocyanines and phthalocyanine-fullerene (Pc- C 60) dyads, in which fullerene is regioselectively attached to phthalocyanine with two linkers, are described. 1 H NMR spectroscopy results clearly indicate an e addition pattern of the fullerene moiety in trans-dyad 9, and apparently a cis-3 addition pattern in cis-dyad 10. The possible spatial arrangements of 9 and 10 were further examined by molecular modeling. The dyads have polar (– OH ) side chains on the fullerene side of the dyad providing a possibility to produce oriented donor–acceptor (D–A) Langmuir monolayers on aqueous subphase, which can be shifted onto a solid surface. When deposited on a solid electrode material, parallel vertical alignment of the phthalocyanine and fullerene moieties in 100% dyad monolayer was obtained and vertical electron transfer from Pc to C 60 upon photoexcitation was demonstrated. Introduction of the dyads as an oriented interfacial monolayer between the photoactive layer and metal anode improved the power conversion efficiency in inverted organic solar cells.

Photophysical insights into fullerene–porphyrazine supramolecular interactions in solution

This communication reports supramolecular interactions of a porphyrazine derivative, namely, 2,7,12,17-tetra-tert-butyl-5,10,15,20-tetraaza-21H,23H-porphine (1) with C₆₀ and C₇₀ in toluene and dichlorobenzene.

Supramolecular electron transfer-based switching involving pyrrolic macrocycles. A new approach to sensor development?

The potential utility of energy transfer in the design of pyrrolic macrocycle-based molecular switches and ability to serve as the readout motif for molecular sensors development is discussed.

Covalent phthalocyanine-fullerene dyads: synthesis, electron transfer in solutions and molecular films

Phthalocyanine-fullerene dyads have being under intensive development and investigation during past decade. Strong absorption of the phthalocyanine chromophore in the red part of the spectrum and ability of the dyad to perform efficient photoinduced charge transfer in non-polar media make them particularly attractive for organic optoelectronic applications. This microreview will focus on covalently linked phthalocyanine-fullerene conjugates in solutions and solid nanostructures. The covalent bonding enables sufficient degree of control over mutual organization of the donor and acceptor parts, and makes possible to investigate the relationships between molecular structure and functioning of single molecules and molecular assemblies.

Aqueous mixtures of di-n-decyldimethylammonium chloride/polyoxyethylene alkyl ether: dramatic influence of tail/tail and head/head interactions on co-micellization and biocidal activity

Mixed aggregate formation and synergistic interactions of binary surfactant mixtures of di-n-decyldimethylammonium chloride, [DiC(10)][Cl], with polyoxyethylene alkyl ethers, C(i)E(j) (i=10, 12, j=4, 6, 8), have been investigated for various [DiC(10)][Cl]/C(i)E(j) ratios. The critical aggregation concentration of the binary mixtures has been determined by tensiometry, and the aggregate characteristics (i.e., size and composition, free ammonium concentration) have been estimated using the pulsed field gradient NMR spectroscopy and a [DiC(10)]-selective electrode. Diffusion coefficient measurements of micelles confirmed the synergistic interaction between the surfactants. It is thus shown that the formation of surface monolayers and mixed aggregates from [DiC(10)][Cl]/C(10)E(j) mixtures is driven by both tail/tail and head/head interactions, whereas [DiC(10)][Cl]/C(12)E(j) co-aggregation is mainly driven by tail/tail interactions. As a consequence, the co-aggregation phenomenon notably influences the biocidal activity of [DiC(10)][Cl] on the Candida albicans fungi. In the presence of C(12)E(j), the biocidal activity of the ammonium salt is inhibited due to the trapping of the cationic surfactants in the mixed aggregates, whereas in the presence of C(10)E(j), the biocidal activity of the surfactant mixture is maintained. The mode of action is also confirmed by a faster increase in the zeta potential of a C. albicans suspension in the presence of [DiC(10)][Cl]/C(10)E(8) than in the presence of [DiC(10)][Cl]/C(12)E(8). Therefore, a judicious adjustment of the alkyl (i) and polyoxyethylene (j) chain lengths of C(i)E(j) avoids its antagonistic effect on the biocidal activity of [DiC(10)][Cl].