Solvent effects on the NMR spectra of symmetrical (X = F (1), X = Cl (2), X = Br (3), X = I (4), X = NO2 (5), X = CN (6)) and unsymmetrical (X = I, Y = MeO (7), Y = PhO (8)) para-disubstituted acetophenone azines X-C6H4-CMe=N-N=CMe-C6H4-Y and of models X-C6H4-CMe=N-Z (X = I, Z = H (9), Z = NH2 (10)), 4-iodoacetophenone (11), and iodobenzene (12) were measured in CDCl(3), DMSO, THF, pyridine, and benzene to address one intramolecular and one intermolecular issue. Solvent effects on the (13)C NMR spectra are generally small, and this finding firmly establishes that the azine bridge indeed functions as a "conjugation stopper," an important design concept in our polar materials research. Since intermolecular halogen bonding of haloarenes do occur in polar organic crystalline materials, the NMR solution data pose the question as to whether the absence of solvent shifts indicates the absence of strong halogen bonding in solution. This question was studied by the theoretical analysis of the DMSO complexes of iodoarenes 4, 9-12, and of iodoacetylene. DFT and MP2 computations show iodine bonding, and characteristic structural and electronic features are described. The nonrelativistic complexation shifts and the change in the spin-orbit induced heavy atom effect of iodine compensate each other, and iodine bonding thus has no apparent effect on Ci in the iodoarenes. For iodides, complexation by DMSO occurs and may or may not manifest itself in the NMR spectra. The absence of complexation shifts in the NMR spectra of halides does not exclude the occurrence of halogen bonding in solution.

The title compound 1,4-(E,E)-diphenylbutadiene crystallizes in the space group P2 1 /n, and the structure contains three independent molecules A-C with modest twisting about the C-Ph bonds. Each molecule engages in two double face-to-face contacts and in four double T-contacts of a new type. These arene-arene interactions form two-dimensional layers that are stacked in the third dimension. In the new double T-contact, both arenes of each laterally off-set spacer-connected diarene serve as faces or edges in each contact. The occurrence of either one independent molecule (A) in two orientations (+A and -A) or of two independent molecules (B and C) results in two diastereoisomeric double T-contacts in each layer. Molecule A is asymmetric and forms enantiomeric (-A+A) and (-A′+A′) layers. The alternation between layers with different pairs of diastereosiomeric double T-contacts allows for reduced surface-matching and better van der Waals interactions between the surfaces of the -A+A (-A′+A′) layers and the BC layers.

Extraordinary high degrees of polar order can be achieved by a rational design that involves the polar stacking of parallel beloamphiphile monolayers (PBAM). This strategy is exemplified by the acetophenone azines MCA (4-methoxy-4'-chloroacetophenone azine) and DCA (4-decoxy-4'-chloroacetophenone azine). The beloamphiphile design aims to achieve strong lateral interactions by way of arene-arene, azine-azine, arene-azine and halogen-bonding interactions. Dipole-induced interactions and halogen bonding dominate interlayer interactions and halogen bonding is shown to effect the layer stacking. Crystals of DCA contain PBAMs with perfect polar order and perfect polar layer stacking, while crystals of MCA features perfect polar order only in one of two layers and layer stacking is polar but not entirely perfect. We report the synthesis of the beloamphiphile DCA, its crystal structure, and we present a comparative discussion of the structures and intermolecular interactions of MCA and DCA. Absorbance and photoluminescence measurements have been carried out for solutions of DCA and for DCA crystals. DCA exhibits a broad emission centered at 2.5 eV when excited with UV radiation. The nonlinear optical response was studied by measuring second harmonic generation (SHG). Strong SHG signals have been observed due to the polar alignment and the DCA crystal's NLO response is 34 times larger than that of urea. Optimization of the beloamphiphile and systematic SAR studies of the polar organic crystals, which are now possible for the very first time, will further improve the performance of this new class of functional organic materials. The materials are organic semiconductors and show promise as blue emitters, as nonlinear optical materials and as OLED materials.

The results are reported of a theoretical study of the addition of small nucleophiles Nu(-) (HO(-), F(-)) to phenylboronic acid Ph-B(OH)(2) and of the stability of the resulting complexes [Ph-B(OH)(2)Nu](-) with regard to Ph-B heterolysis [Ph-B(OH)(2)Nu](-) --> Ph(-) + B(OH)(2)Nu as well as Nu(-)/Ph(-) substitution [Ph-B(OH)(2)Nu](-) + Nu(-) --> Ph(-) + [B(OH)(2)Nu(2)](-). These reactions are of fundamental importance for the Suzuki-Miyaura cross-coupling reaction and many other processes in chemistry and biology that involve phenylboronic acids. The species were characterized by potential energy surface analysis (B3LYP/6-31+G*), examined by electronic structure analysis (B3LYP/6-311++G**), and reaction energies (CCSD/6-311++G**) and solvation energies (PCM and IPCM, B3LYP/6-311++G*) were determined. It is shown that Ph-B bonding in [Ph-B(OH)(2)Nu](-) is coordinate covalent and rather weak (<50 kcal.mol(-1)). The coordinate covalent bonding is large enough to inhibit unimolecular dissociation and bimolecular nucleophile-assisted phenyl anion liberation is slowed greatly by the negative charge on the borate's periphery. The latter is the major reason for the extraordinary differences in the kinetic stabilities of diazonium ions and borates in nucleophilic substitution reactions despite their rather similar coordinate covalent bond strengths.

4'-Acetyl-4-methoxy-biphenyl (AMB) was synthesized via catalytic Suzuki cross-coupling reaction and the crystal structure was determined. The crystals of AMB feature an orthorhombic unit cell with a = 7.900(6) A, b = 5.429(4) A, and c = 26.80(2) A and the crystals are noncentrosymmetric, space group Pna2(1). The crystal structure of AMB features parallel-alignment of essentially planar molecules in the syn-conformation with molecular dipole moments of about 5.4 Debye and affords about 53% of maximal polar alignment. The polar crystal structure of syn-AMB contrasts with the nonpolar crystal structure of the homologue 4-methoxyacetophenone syn-MAP. The fundamental difference between the packing motives of AMB and MAP is explained on the basis of lateral arene-arene interactions. The lattice architecture of AMB is compared to the motives realized in the only two other parallel-aligned polar biphenyls, 4'-n-butoxy-4-cyanobiphenyl (nBCB) and 4'-dimethylamino-4-cyanobiphenyl (DMACB). The analysis provides conceptual insights to guide the rational design of polar materials and several resulting hypotheses are stated explicitly and can be tested.