Syntheses, crystal structures, ab initio density functional theory computations, and photophysical properties of 1,6-di-, 1,2,5,6-tetra-, and 1,3,5,7,9-pentaethynyl-substituted corannulenes (classes 3, 4, and 5, respectively) are reported. Classes 3 and 4 were prepared from the corresponding corannulenyl bromides and terminal alkynes in excellent yields (nine examples, with yields of 57-92%) using the Sonogarshira reaction. Class 5 was prepared from 1,3,5,7,9-pentacholorocorannulene and trimethylalkynylstannanes using a modification of Nolan's procedure (8 examples, with yields of 45-93%). The molecular packing in crystals of 1,6-diphenylethynyl-2,5-dimethylcorannulene (3-Ph2) displays a polar columnar structure with all of the molecule bowls oriented in the same direction. Similarly, 1,2,5,6-tetrakis(3,5-dimethylphenylethynyl)corannulene [4-Ar(c)5] and 1,3,5,7,9-pentakis(3,5-dimethylphenylethynyl)corannulene [5-Ar(c)5] form columnar structures, but the bowls are oriented in opposing directions. Additionally, the number of attached alkynyl arms is correlated with an increase in bowl depth of the corrannulene nucleus. Most of the aryl derivatives displayed high-quantum-efficiency solution luminescence and variable emission wavelengths that were dependent on the nature of the substitution.

Concepts of close packing in monolayers of 5-fold-symmetric buckybowls are discussed. When the symmetry of lattice and molecular building blocks are incompatible, new strategies evolve. Corannulene forms a hexagonal lattice on Cu(111) by tilting away from the C(5) symmetry and aligning one hexagonal ring parallel to the surface. The chiral 5-fold-substituted chloro and methyl derivatives do not show this tilt and maintain the 5-fold symmetry as adsorbates. Consequently, a nonperfect tiling is observed. Their lattices are quasi-hexagonal: one in an antiparallel fashion with almost pm symmetry and the other with azimuthal and positional disorder on the hexagonal grid. Our results are in remarkable agreement with computational and mechanical modeling experiments of close packing of hard pentagonal discs in macroscopic two-dimensional systems and prove the validity of such modeling strategies.

The functionalization of cubosomes with biotin is reported here as an alternative method for the preparation of drug delivery systems capable of active targeting specific receptors that are (over)expressed by cancer cells. We describe the design, synthesis, assembly, and characterization of these novel cubosome nanoparticles by small-angle X-ray scattering (SAXS) and dynamic laser light scattering (DLS) and show their application to human adenocarcinoma cell line HeLa. These cubosomes are stabilized and functionalized with a novel, designed biotin-based block copolymer and are able to simultaneously transport paclitaxel, a potent anticancer drug, and a hydrophobic fluorescent dye in the active targeting of cancer cells. Such biotinylated cubosomes are potentially applicable in diagnosis, drug delivery, and monitoring of the therapeutic response for active targeting versus cancer cells.

Dedicated to Professor Franco Cozzi on the occasion of his 60th birthdayNumerous stereoselective catalytic processes rely on the differentiation of internally enantiotopic faces of planar psystems by metal complexation.[1] Chiral bowl-shaped molecules like 1,3,5,7,9-pentasubstituted corannulene, which invert rapidly on the reaction timescale, present themselves as achiral due to tautomeric equilibration of enantiomers, [2] and thereby display externally enantiotopic p-faces.[3] Stereoselective complexation of one such p-face shifts the tautomeric equilibrium and offers the possiblity to effect a complete dynamic resolution.[4] Thus, such systems provide a special platform for studying chiral ligand-metal molecular recognition and metal-arene complex dynamics.The hydrogens in one bowl form of corannulene (1) are chirotopic and segregate into two internally enantiotopic sets of five homotopic hydrogens; the endo and exo faces of the bowl are diastereotopic. Bowl inversion renders all hydrogens, and the two faces, respectively homotopic. Under conditions of bowl inversion, simple metal coordination to either face of corannulene is not an event wherein stereoselection can occur (the products are homomeric). In contrast, sym-pentasubstituted corannulenes, such as 1,3,5,7,9-pentamethylcorannulene (2), oscillate between enantiomeric C 5 -symmetric bowl conformations (Figure 1). The hydrogens of these conformers are internally homotopic but externally enantiotopic; the faces are diastereotopic in the static bowl, and rendered enantiotopic by inversion. Simple metal complexation of 2 yields enantiomeric products, whereby enantioselection becomes possible. [5] From this stereochemical analysis, 1) complexation of 1 with a racemic metal fragment should yield two enantiomeric products with diastereotopic hydrogen NMR signals from corannulene, 2) complexation of 2 with a metal bearing enantiotopic hydrogens should yield enantiomeric products with diastereotopic hydrogen NMR signals coming from the metal fragment, and 3) complexation of 2 with an enantiomerically pure metal fragment should lead to diastereoselective chiral complex formation that effectively resolves the bowl forms of 2 into 100 % of a single chiral diastereomer. Each of these complexes provides an unambiguous way to follow the dynamics of metal-arene rotation, migration, and transfer from a single complex. [6] The corannulene partners in this study include 1, 2, [7] and 1,3,5,7,9-penta-tert-butylcorannulene (3).[8] On the metal side, the fragments include {Rh(nbd)} + (nbd = bicyclo[2.2.1]hepta-2,5-diene), in reagent form as [{(nbd)RhCl} 2 ] (4), and {Rh-(nbd*)} + (nbd* = C 2 -symmetric (R,R)-2,5-dimethyl-bicyclo-[2.2.1]hepta-2,5-diene), in reagent form as [{(nbd*)RhCl} 2 ] (5).[9] Reaction of a corannulene and a [{(nbd)RhCl} 2 ] derivative activated by silver(I) in dichloromethane at room temperature produces the expected complexes 6-9 (Scheme 1).Complexation of 1 with 5 to yield 6 exemplifies the first case from the above stereochemical analysis. At the stat...