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Meso-5,10,15,20-tetrakis-3,5-di-tert-butyl-4-oxocyclohexadienylideneporphyrinogen, OxP, is a versatile, highly colored chromophore with strong broad absorption in the visible range. It is derived from meso-5,10,15,20-tetrakis(3,5-di-tert-butyl-4-hydroxyphenyl)porphyrin by two-electron oxidation, and the OxP tetrapyrrole moiety exists in a saddle conformation. N-Alkylation of the OxP core nitrogen atoms can be used to functionalize the chromophore leading to a class of stable molecules with highly substituted peripheries. Substituted OxPs can act as singlet oxygen generators under light irradiation and the efficacy of this process is influenced by the multiplicity of N-substitution, and by the chemical identity of those substituents. Bromination of the macrocyclic [Formula: see text]-positions can also be used to control singlet oxygen generation by the relevant derivatives. We report the quantum yields of singlet oxygen generation for a series of differently substituted OxP derivatives whose metrics indicate that these compounds possess significant potential in the corresponding applications including photodynamic therapy, bacterial inactivation therapy, and organic transformations.

A novel fused porphyrinoid undergoes supramolecular assembly to form a persistently porous solution processable material for sensing of acetone vapour under high humidity using a membrane-type surface stress sensor.

Molecular rotors are an important class of dynamic molecules which have been studied not only for their possible uses as components of molecular machines but also because of potential applications as probes of local viscosity in biological media, especially self-assembled membranes. For the former, factors affecting rotational motility are critical while for the latter the rotor activity must be complexed with an output signal (often fluorescence) for reporting of local conditions. Molecular single stator-double rotor activity of an oxidized resorcinarene (fuchsonarene) macrocycle containing unsaturated hemiquinonoid groups at its meso positions was investigated. Fuchsonarenes contain two hemiquinonoid substituents at diagonally-opposed meso-positions with two electron rich phenol groups at the remaining meso-positions between the hemiquinonoid groups. All meso-substituents are in proximity at one side of the resorcinarene macrocycle (so-called rccc-type isomer) with rotational activity of the phenol meso-substituents. Rotation rates of the phenol moieties can be controlled by varying temperature, solvent polarity and acidity of the medium of study with rotation being thermally activated in neutral and acidic media and tunable in the range from 2 s−1 to 20 000 s−1. Experimental and computational data indicate that rotation of the mobile phenol meso-substituents is remotely affected by interactions with acidic solvents at the carbonyl CO groups of macrocyclic acetyloxy groups, which occurs with the emergence of a lower energy electronic absorption band whose intensity is correlated with both the acidity of the medium and the rotation rate of the phenol substituents. Time-dependent DFT calculations suggest that the low energy band is due to a molecular conformational adjustment affecting electronic conjugation caused by strong interaction of macrocyclic acetyloxy carbonyl groups with the acid medium. The work presents a molecular mechanical model for estimating solution acidity and also gives insight into a possible method for modulating rotor activity in molecular machines.

Designing fluorescent molecules requires considering multiple interrelated molecular properties, as opposed to properties that straightforwardly correlated with molecular structure, such as light absorption of molecules. In this study, we have used a de novo molecule generator (DNMG) coupled with quantum chemical computation (QC) to develop fluorescent molecules, which are garnering significant attention in various disciplines. Using massive parallel computation (1024 cores, 5 days), the DNMG has produced 3643 candidate molecules. We have selected an unreported molecule and seven reported molecules and synthesized them. Photoluminescence spectrum measurements demonstrated that the DNMG can successfully design fluorescent molecules with 75% accuracy ( n = 6/8) and create an unreported molecule that emits fluorescence detectable by the naked eye.