Contrasting Photodynamics between C60-Dithiapyrene and C60-Pyrene Dyads

Decarboxylative 1,3-dipolar cycloaddition of amino acids for the synthesis of heterocyclic compounds

The [3 + 2] cycloadditions of stabilized azomethine ylides (AMYs) derived from amino esters are well-established. However, the reactions of semi-stabilized AMYs generated from decarboxylative condensation of α-amino acids with arylaldehydes are much less explored. The [3 + 2] adducts of α-amino acids could be used for a second [3 + 2] cycloaddition as well as for other post-condensation modifications. This article highlights our recent work on the development of α-amino acid-based [3 + 2] cycloaddition reactions of N-H-type AMYs in multicomponent, one-pot, and stepwise reactions for the synthesis of diverse heterocycles related to some bioactive compounds and natural products.

Emission Energies and Stokes Shifts for Single Polycyclic Aromatic Hydrocarbon Sheets in Comparison to the Effect of Excimer Formation

Emission spectra of paradigmatic single-sheet polycyclic aromatic hydrocarbons (PAHs), pyrene, circum-1-pyrene, coronene, circum-1-coronene, and circum-2-coronene and Stokes shifts were computed and compared with previously calculated comparable data for relaxed excimer structures using the SOS-ADC(2), TD-B3LYP, and TD-CAM-B3LYP methods with multireference DFT/MRCI data as the benchmark. Vertical emission transitions and Stokes shifts were extrapolated to infinite PAH size. Comparison of Stokes shifts computed from theoretical monomer and dimer data confirms assumptions that relaxed excimers are responsible for the unusually large Stokes shifts in carbon dots observed in experimental investigations.

Sulfhydryl-Directed Iridium-Catalyzed C-H/Diazo Coupling and Tandem Annulation of Naphthalene-1-thiols

The first sulfhydryl-directed iridium-catalyzed C-H/diazo coupling and tandem annulation of naphthalene-1-thiols has been developed. The framework of naphtho[1,8-bc]thiopyrans was constructed in a one-step reaction with good yields. This transformation provides a practical synthetic route for the widely used naphtho[1,8-bc]thiopyran derivatives.

A porous, electrically conductive hexa-zirconium(iv) metal-organic framework

Engendering electrical conductivity in high-porosity metal-organic frameworks (MOFs) promises to unlock the full potential of MOFs for electrical energy storage, electrocatalysis, or integration of MOFs with conventional electronic materials. Here we report that a porous zirconium-node-containing MOF, NU-901, can be rendered electronically conductive by physically encapsulating C60, an excellent electron acceptor, within a fraction (ca. 60%) of the diamond-shaped cavities of the MOF. The cavities are defined by node-connected tetra-phenyl-carboxylated pyrene linkers, i.e. species that are excellent electron donors. The bulk electrical conductivity of the MOF is shown to increase from immeasurably low to 10-3 S cm-1, following fullerene incorporation. The observed conductivity originates from electron donor-acceptor interactions, i.e. charge-transfer interactions - a conclusion that is supported by density functional theory calculations and by the observation of a charge-transfer-derived band in the electronic absorption spectrum of the hybrid material. Notably, the conductive version of the MOF retains substantial nanoscale porosity and continues to display a sizable internal surface area, suggesting potential future applications that capitalize on the ability of the material to sorb molecular species.

A study of planar anchor groups for graphene-based single-molecule electronics

To identify families of stable planar anchor groups for use in single molecule electronics, we report detailed results for the binding energies of two families of anthracene and pyrene derivatives adsorbed onto graphene. We find that all the selected derivatives functionalized with either electron donating or electron accepting substituents bind more strongly to graphene than the parent non-functionalized anthracene or pyrene. The binding energy is sensitive to the detailed atomic alignment of substituent groups over the graphene substrate leading to larger than expected binding energies for -OH and -CN derivatives. Furthermore, the ordering of the binding energies within the anthracene and pyrene series does not simply follow the electron affinities of the substituents. Energy barriers to rotation or displacement on the graphene surface are much lower than binding energies for adsorption and therefore at room temperature, although the molecules are bound to the graphene, they are almost free to move along the graphene surface. Binding energies can be increased by incorporating electrically inert side chains and are sensitive to the conformation of such chains.

Synthesis of mesogenic phthalocyanine-C60 donor-acceptor dyads designed for molecular heterojunction photovoltaic devices

A series of phthalocyanine-C₆₀ dyads 2a–d was synthesized. Key steps in their synthesis are preparation of the low symmetry phthalocyanine intermediate by the statistical condensation of two phthalonitriles, and the final esterification of the fullerene derivative bearing a free COOH group. Structural characterization of the molecules in solution was performed by NMR spectroscopy, UV–vis spectroscopy and cyclic voltammetry. Preliminary studies suggest formation of liquid crystalline (LC) mesophases for some of the prepared dyads. To the best of our knowledge, this is the first example of LC phthalocyanine-C₆₀ dyads.