New Crystal Form of an Organic Nonlinear Optical Material, 8-(4‘-Acetylphenyl)-1,4-dioxa-8-azaspiro[4.5]decane (APDA)

A new crystal form of an organic nonlinear optical material, 8-(4‘-acetylphenyl)-1,4-dioxa-8-azaspiro[4.5]decane (APDA) was found in the crystal growth by plate sublimation. This new crystal structure belongs to the noncentrosymmetric class, orthorhombic P 2 1 2 1 2 1, and the unit-cell dimensions are a = 8.428 (8) Å, b = 28.349 (3) Å, c = 5.634 (2) Å, V = 1346.0 (6) Å 3, Z = 4, which are different from previously reported, orthorhombic Pna 2 1 . The molecule in the P 2 1 2 1 2 1 crystal has less twisting and more bending in the structure than in Pna 2 1 . The APDA molecules are coupled in an antiparallel system in the P 2 1 2 1 2 1 crystal as if to compensate for the repulsion arising from dipole−dipole interactions. This is in contrast to the molecular alignment of the Pna 2 1 crystal in which the molecules are arranged in the same direction. The molecular hyperpolarizabilities (β) and d coefficients of the new crystal form were investigated theoretically by semiempirical CNDO/S-CI.