This study focuses on the Baeyer-Villiger reaction of propanone and performic acid, with formic acid as catalyst. Continuum solvation methods (EIF-PCM and CPCM) and two density functionals (B3LYP and MPWB1K) are used to study solvent effects on two types of reaction mechanisms: concerted non-ionic and stepwise ionic. The ionic mechanism is the one found in most organic chemistry textbooks; it begins with the protonation of the ketone by the acid catalyst, even though this reaction normally takes place in non-polar solvents such as dichloromethane. Our calculations show that the concerted non-ionic pathway, which is the least energetic in non-polar solvents such as dichloromethane, becomes more energetic the more polar the solvent. After investigating a variety of non-ionic and ionic pathways in water, it is found that the addition step seems to be ionic but the migration step, which is rate-determining, is uncatalyzed, non-ionic and fully concerted. These results confirm the experimental findings in solvents of low to medium polarity that the rate constant of the reaction decreases as the solvent polarity increases. Moreover, we find that contrary to what is commonly accepted, in the addition and migration ionic steps the deprotonation of the ionic species occurs in a concerted manner with the other chemical events taking place.

It is uncommon to read about cyanine dyes in the literature and not have their aggregation discussed. They are of high interest considering their propensity to undergo self-organization in aqueous solution, leading to interesting photophysical properties resulting from the formation of their dimers and higher ordered aggregates. Currently, the study of their aggregation is in high demand due to their diverse application range including dye-sensitized solar cells. However, their aggregation in high salt solutions is under studied, and the effect on aggregation in congruence with high ionic strength is often overlooked. In a previous study, our group established the role of specific ion effects and in particular the necessity of matching water affinity to induce aggregation of a cationic cyanine dye, thiazole orange. In order to advance the understanding of this topic, we present in this article the diverse aggregation of cyanine dyes, as a single monovalent salt can cause different aggregation responses in a variety of these dyes. We established via absorption spectroscopy combined with chemometric analyses that the inherent monomer-dimer equilibrium of a dye depends on its geometry. More interestingly, experimental data coupled with DFT calculations reveal that not only the geometry of a dye but also its charge location plays a role in the aggregate morphology formed by the interaction of a cationic cyanine dye and an anion. It is thought that contact ion pair formation and effective charge screening generated within that ion pair are responsible for aggregates with a greater order.

Three isomeric donor-acceptor (DA) chromophores based on pyrene were synthesized to study the effects of substitution pattern on intramolecular charge-transfer absorption through pyrene. These chromophores are nonfluorescent and absorb light in the long-wavelength region approaching 700 nm, making them promising light-harvesters. Their optical properties depend greatly on the substitution pattern of the donor, but their electrochemical properties are relatively unaffected.

Three donor–acceptor–donor (D–A–D) pyrene chromophores are described and compared by DFT computations. The two properties of low energy photon absorption and low energy electrochemical reduction are demonstrated through a pyrene framework. Altering the electron‐acceptor strength of the pyrene core by chemical oxidation or installation of a thiadiazole dioxide heterocycle results in the formation of D–A–D chromophores with absorption bands up to 900 nm and LUMO energy levels of approximately –4.1 eV vs. vacuum.

The ability to form self-organized thermotropic mesophases of amphiphilic cyclodextrins correlates well with their ability to establish an intermolecular H-bond network.

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21,23-Dithiaporphyrins were synthesized containing pi-extending ethynyl substituents at the meso positions. These porphyrins displayed highly bathochromic and broadened absorbance profiles spanning 400-900 nm with molar absorptivities ranging from 2500 to 300,000 M(-1) cm(-1). Electrochemically, these ethynyl dithiaporphyrins undergo a single oxidation at 0.44 or 0.57 V and reduction at -1.17 or -1.08 V versus a ferrocene/ferrocenium internal standard depending on the type of functionalization appended to the ethynyl group. DFT calculations predict that the delocalization of the frontier molecular orbitals should expand onto the meso positions of the ethynyl 21,23-dithiaporphyrins; shrinking the HOMO-LUMO energy gap by destabilizing the HOMO energy. Indeed, the DFT results agree with our optical and electrochemical assessments. Finally, differential scanning calorimetry combined with cross-polarized optical microscopy and powder X-ray diffraction was used to assess the ability of these porphyrins for long-range order. For the ethynylphenyl alkoxy 21,23-dithiaporphyin, birefringent, soft-crystalline-like domains were observed by polarized microscopy, which are marginally sustained by a low-level of crystallinity detected in the XRD, suggesting that long-range ordering is possible. Overall, ethynyl 21,23-dithiaporphyrins are able to harvest much lower energy light and possess lower oxidation and reduction potentials compared to their pyrrolic analogues, which are desirable properties for applications in organic electronics.

Near-IR absorbing, self-assembling pyrene donor–acceptor chromophore with low reduction potentials.