Structure−Property Relationship for Two-Photon Absorbing Multiporphyrins: Supramolecular Assembly of Highly-Conjugated Multiporphyrinic Ladders and Prisms

Switching the Photoluminescence and Electrochemiluminescence of Liposoluble Porphyrin in Aqueous Phase by Molecular Regulation

By a facile peripheral decoration of 5-(4-aminophenyl)-10,15,20-triphenylporphyrin (ATPP) with inherent aggregation-induced emission (AIE) active tetraphenylethene (TPE), a versatile AIEgenic porphyrin derivative (ATPP-TPE) was obtained, which greatly abolishes the detrimental π-π stacking and thus surmounts the notorious aggregation-caused quenching (ACQ) effect of ATPP in aqueous phase. The photoluminescence of ATPP-TPE is 4.5-fold stronger than ATPP at aggregation state. Moreover, an unequivocal aggregation induced electrochemiluminescence (AIECL) of ATPP-TPE was found to be seriously dependent on its aggregation property in aqueous solution with efficiency of 34 %, which is 6 times higher than pure ATPP. The versatility of this molecular structure modulation strategy along with the ACQ-to-AIE transformation in this work provides direction to guide for applying liposoluble porphyrins in aqueous phase by designs of synthetic porphyrin AIEgens.

A Coarse-Grained Model for Free and Template-Bound Porphyrin Nanorings

Coarse-grained simulation models are developed to study both template-bound and free porphyrin nanoring systems. Key interactions are modeled with relatively simple (and physically motivated) energy functions which allow for relatively facile transfer both between different ring sizes and between the template-bound and free nanoring systems. The effects of varying the model parameters on the respective radii of gyration are determined. The effects of including different templates on the ring structure are investigated both in terms of the detailed geometry of the template and the interaction strength between the template and the metal centers in the nanorings. The role of the template-nanoring interaction strength in controlling potential "caterpillar track" rotational motion is discussed. The relationship of the model to experimental small-angle X-ray, exchange spectroscopy, and electron spin resonance results is discussed.

Structure-Dependent Electronic Interactions in Ethyne-Bridged Porphyrin Arrays Investigated by Single-Molecule Fluorescence Spectroscopy

By using single-molecule fluorescence spectroscopy, we have investigated the electronic interaction of ethyne-bridged porphyrin arrays (ZNE) depending on their structure. The fluorescence dynamics of ZNE show a large amount of one-step photobleaching behaviors, indicating the high degree of π-conjugation. The ratio of one-step photobleaching behavior decreased as the number of porphyrin units increased. This behavior indicates that the linear and shortest Z2E shows a strong electronic coupling between constituent porphyrin moieties. Structural properties and orientation of ZNE were also measured by wide-field excitation fluorescence spectroscopy (ExPFS) and defocused wide-field imaging (DWFI). The ExPFS and DWFI show that the structure of absorbing and emitting units of Z2E and Z3E are linear. On the other hand, star-shaped pentamer with five porphyrins acts as an absorbing unit, but unidirectional trimer moiety acts as an emitting unit in the Z5E molecule. Collectively, these studies provide further information on the electronic interaction depending on their structure and length.

Photogenerated triplet states in supramolecular porphyrin ladder assemblies: an EPR study

Ladder formation and planarisation do not enhance delocalisation in the triplet excited states of linear porphyrin oligomers.

Strongly conjugated hydroporphyrin dyads: extensive modification of hydroporphyrins' properties by expanding the conjugated system

We report the synthesis and basic photophysical characterization of strongly conjugated hydroporphyrin (chlorin and bacteriochlorin) dyads. Hydroporphyrins are connected at their respective 13 (β) or 15 (meso) positions by ethynyl or butadiynyl linkers. Synthesis entails a series of palladium-catalyzed reactions, starting from appropriate bromobacteriochlorin or bromochlorin. Strong conjugation in the dyads results in a significant bathochromic shift of longest-wavelength (Qy-like) band, which in case of the 13-13' ethynyl-linked bacteriochlorin dyad is positioned past 800 nm. The Qy-like band is broad and split for the 13-13' linked chlorin and bacteriochlorin dyads. All dyads exhibit an intense, relatively narrow fluorescence emission band in nonpolar solvents. Bacteriochlorin dyads exhibit a strong dependence of fluorescence intensity on the solvent polarity, which results in more than 10-fold quenching of fluorescence in dimethylformamide. The assembling of hydroporphyrins into strongly conjugated arrays represents an efficient means to tune and expand their optical and photochemical properties, which should greatly broaden the properties attainable for these chromophores.

Photophysics of glycosylated derivatives of a chlorin, isobacteriochlorin and bacteriochlorin for photodynamic theragnostics: discovery of a two-photon-absorbing photosensitizer

The photophysical properties of a chlorin, isobacteriochlorin and bacteriochlorin built on a core tetrapentafluorophenylporphyrin (TPPF20 ) and the nonhydrolyzable para thioglycosylated conjugates of these chromophores are presented. The photophysical characterization of these compounds was done in three different solvents to correlate with different environments in cells and tissues. Compared with TPPF20 other dyes have greater absorption in the red region of the visible spectrum and greater fluorescence quantum yields. The excited state lifetimes are from 3 to 11 ns. The radiative and nonradiative rate constants for deactivation of the excited state were estimated from the fluorescence quantum yield and excited state lifetime. The data indicate that the bacteriochlorin has strong absorption bands near 730 nm and efficiently enters the triplet manifold. The isobacteriochlorin has a 40-70% fluorescence quantum yield depending on solvent, so it may be a good fluorescent tag. The isobacteriochlorins also display enhanced two-photon absorption, thereby allowing the use of 860 nm light to excite the compound. While the two-photon cross section of 25 GM units is not large, excitation of low chromophore concentrations can induce apoptosis. The glycosylated compounds accumulate in cancer cells and a head and neck squamous carcinoma xenograft tumor model in mice. These compounds are robust to photobleaching.

Supramolecular self-assemblies as functional nanomaterials

In this review, we survey the diversity of structures and functions which are encountered in advanced self-assembled nanomaterials. We highlight their flourishing implementations in three active domains of applications: biomedical sciences, information technologies, and environmental sciences. Our main objective is to provide the reader with a concise and straightforward entry to this broad field by selecting the most recent and important research articles, supported by some more comprehensive reviews to introduce each topic. Overall, this compilation illustrates how, based on the rules of supramolecular chemistry, the bottom-up approach to design functional objects at the nanoscale is currently producing highly sophisticated materials oriented towards a growing number of applications with high societal impact.