Bent-core or banana-shaped liquid crystal mesogens are known to form chiral smectic phases from achiral or racemic molecules, representing the first example of conglomerate formation in bulk fluids. The most well studied examples of this behavior occur in the SmCP phases, subphases possessing the B2 chiral layer structure. However, the first description of chirality in the banana phase space was of the B4 phase, whose detailed structure is still under investigation. Indeed, the B4 phase is quite unique, and a consensus regarding the question of whether this phase is crystalline or liquid crystalline has not been reached. Here we describe data showing distinct differences, by NMR, between the SmCP phase and B4 phase of the prototypical banana phase mesogen NOBOW and, based upon an analysis of these data, suggest that the B4 phase is an unusual type of crystalline solid.

Phenyl-perisubstituted benzenes, tetraphenylbenzene (1) and hexaphenylbenzene (2), were reduced by lithium and sodium metal in THF-d 8 under high vacuum. The reduction process and the nature of the reduction products were studied by NMR. Tetraphenylbenzene was reduced by both metals to yield the corresponding dianionic salt. It was found that the addition of extra charge into the system, restricted the free rotation of the four phenyl substituents about the σ bond connecting them to the central ring (G q 181 ) 7.8 ( 0.2 kcal mol -1 ). The reaction of the alkali metals with 2 yielded four diamagnetic species: the first three were assigned to the dianion, tetraanion, and the surprising hexaanion of 2. These species were calculated using density functional theory (DFT) and were found to have central benzene rings with an unusual twist-boat geometry. Computational and experimental evidences show that each phenyl ring and its attached carbon of the central ring behave like a benzyl anion. We therefore view the hexaanion of 2 as a cyclohexa(benzylanion). The fourth diamagnetic species was a product of a double-sided cyclization, which yielded the dianion of dihydro-9,18-diphenylphenanthro[9,10-b]triphenylene (9,18-diphenyltetrabenz[a,c,h,j]anthracene dianion, 3 2-). Reaction of the dianion with oxygen gave 3 in improved yields compared to literature preparations.

Modern transition-metal-catalyzed cross-coupling reactions, especially of the Kumada, Heck, and Suzuki types, have provided facile access to various bridge-annelated [2.2]paracyclophane derivatives including trifoliaphane and its tribenzo analog. The reduction of trifoliaphane with potassium metal in [D8]-THF led to hexakis[p-benzyl]benzene anion, which could efficiently be trapped with various electrophiles. Highly efficient multifold Suzuki couplings were performed with hexabromobenzene, octabromonaphthalene, and hexabromotriphenylene. The obtained hexa- and octaalkenylarene derivatives disclose interesting molecular shapes. Eventually, a newly developed cascade coupling of bromoarenes containing peri-positioned C-H bonds has led to indeno-annelated polycyclic aromatic hydrocarbons including indenocorannulene as well as the tetrakis- and tris(tert-butylindeno)pyrene which disclose very interesting spectroscopic properties. In particular, tetrakis(tert-butylindeno)pyrene self-assembles in solution by way of π-stacking, and it can be reduced with potassium metal to a stable dianion, a readily dimerizing trianion radical, and a tetraanion.

Various cross-conjugated enediynes undergo "Bergman-type" cycloaromatizations upon reduction with potassium metal, generating anions of fulvenes and fulvalene derivatives. This new anionic cyclization is considerably more facile than the classic Bergman cyclization with linear enediynes, creating highly reactive diradicals at -78 degrees C. Not all cross-conjugated enediynes yield cyclized dianions upon reduction; some give uncyclized, Y-shaped, cross-conjugated dianions, while others apparently yield radical-anions that either dimerize or persist as monomers. One system yields both a cyclized and an uncyclized dianion. The substituents are thus shown to be a critical factor in determining the outcome of the reduction. Cyclization occurs within a specific "window of opportunity" that is governed by the substituents.