Dipole Parallel Alignment in the Crystal Structure of a Polar Biphenyl: 4'-Acetyl-4-Methoxybiphenyl (AMB)
4'-Acetyl-4-methoxybiphenyl (AMB) was synthesized via a 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) Å, b = 5.429(4) Å, and c = 26.80(2) Å, and the crystals are noncentrosymmetric, space group Pna21. The crystal structure of AMB features parallel alignment of essentially planar molecules in the syn conformation with molecular dipole moments of about 5.4 D 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.
R. Glaser et al., "Dipole Parallel Alignment in the Crystal Structure of a Polar Biphenyl: 4'-Acetyl-4-Methoxybiphenyl (AMB)," Crystal Growth and Design, vol. 6, no. 1, pp. 235-240, American Chemical Society (ACS), Jan 2006.
The definitive version is available at https://doi.org/10.1021/cg050316o
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