Theoretical Calculations of the Electronic Absorption Spectra of Oxotitanium(IV) Phthalocyanine in the Solid State

Soft Crystals: Flexible Response Systems with High Structural Order

A new material concept of soft crystals is proposed. Soft crystals respond to gentle stimuli such as vapor exposure and rubbing but maintain their structural order and exhibit remarkable visual changes in their shape, color, and luminescence. Various interesting examples of soft crystals are introduced in the article. By exploring the interesting formation and phase-transition phenomena of soft crystals through interdisciplinary collaboration, new materials having both the characteristics of ordered hard crystals and those of flexible soft matter are expected.

Solution Processed Titanyl Phthalocyanines as Donors in Solar Cells: Photoresponse to 1000 nm

We report a route to thin-film polymorphs of soluble TiOPc derivatives that exhibit similar near-IR absorptivities as vapor deposited thin-films of the parent TiOPc chromophore (phase-I and phase-II polymorphs) and demonstrate that solution-processed planar and bulk heterojunction solar cells fabricated with one of these derivatives exhibited photoactivity throughout the same near-IR wavelength range without compromising VOC. Solution-processed thin-films of soluble octakis(alkylthio)-substituted TiOPc derivatives 1-3 exhibit absorption extending to 1000 nm. When incorporated into OPV devices, the contributions from the lowest CT excitonic state (QB band) of 1 to device performance were evident in both PHJ and BHJ architectures, indicating sufficient driving force for PIET. This contribution was improved via intimate mixing of donor and acceptor molecules in a BHJ architecture, albeit with a decrease in efficiency. IPCE of the best performing BHJ device revealed a contribution from 1 exceeding that of acceptor PCBM, and extending to 1000 nm.

Electronic absorption, MCD, and luminescence properties of porphyrin J-aggregates

In this paper, we have investigated electronic absorption, magnetic circular dichroism, fluorescence, and phosphorescence spectra for a protonated form of H 2 TPPS 4( H 4 TPPS 4) and the J-aggregates of H 4 TPPS 4. The J-aggregation induces a large red-shift in the B (Soret) and Q absorption bands, while the phosphorescence peaks of H 4 TPPS 4 and its J-aggregates are almost entirely similar. The large red-shift of the B-band is quantitatively explained by the exciton interactions. Thus, the exciton interactions in the J-aggregates are proposed as a useful approach to decrease the energy splitting between the fluorescent and phosphorescent states.

The Excited Triplet State Properties of Titanyl Phthalocyanine and its Sulfonated Derivatives

Titanyl phthalocyanine (TiOPc) is a well-known, excellent photoconductive material for laser printers and photocopying machines. Its organic derivatives have recently been shown to be excellent photosensitizers for singlet oxygen [O2(1Δg)] production. The excited triplet state properties of TiOPc, in homogeneous DMSO solution, were measured in this study for the first time by nanosecond laser flash photolysis. The data enabled comparisons to be drawn with TiOPcS4 and zinc phthalocyanine (ZnPc), ultimately providing a better understanding of the reported observations. Absorption, fluorescence, and O2(1Δg) sensitization were also studied. TiOPcS4 in DMSO shows remarkably different fluorescence properties from that reported in aqueous solution: both the fluorescence quantum yield (Φf = 0.068) and the fluorescence lifetime (τf = 3.71 ns) were much larger than that reported for aqueous solutions (0.012 and 0.09 ns, respectively). The photosensitizing properties of TiOPcS4 in DMSO are also so significantly better than that in aqueous solution, i.e. triplet lifetime (τT) of 252 μs, triplet quantum yield (ΦT) of 0.42, and the quantum yield of O2(1Δg) (ΦΔ) of 0.49; compare with values of 60 μs, 0.32, 0.13 reported in aqueous solution. TiOPc, however, shows comparable photophysical properties to that of ZnPc, a well-recognized photosensitizer. These results suggest that TiOPc and its derivatives are not only good photoconductors but also good photosensitizers of O2(1Δg), which may find application in photodynamic therapies for treatment of cancer.

Tuning J-type dimers of non-peripherally substituted zinc tetra-4-tert-butylphenophthalocyanine

It was found, by UV-vis and TOF-MS, that the head-to-tail dimers of non-peripherally substituted zinc tetra-4-tert-butylphenophthalocyanine are inclined to form in non-coordinated solvent, e.g. chloroform and especially in dilute solution under 1.25 x 10(-6)mol/mL. The aforementioned dimers in solution can be tuned by altering concentration or adding coordinated solvent, e.g. methanol, which might be further improved to a practical strategy for preparation of J-aggregates in the future.