Cocrystals of 2-AMINO-5-Nitropyridine with Benzenesulfonic Acids for Second-Order Nonlinear Optical Materials

Abstract

Cocrystals were prepared from 2-amino-5-nitropyridine (2A5NP) and achiral benzenesulfonic acids (Ar–SO3H), which were designed for second-order nonlinear optical materials. Both components are commonly crystallized in 1:1 ionic forms of 2A5NPH+ · Ar–SO3 −. The cocrystal of 2A5NP with 2-nitrobenzenesulfonic acid belongs to acentric space group Pc, in which 2A5NPH+ cation and anion alternately stacked in almost parallel and superimposed manner to form column and layer structures. The cocrystal of 2A5NP with 3-nitrobenzenesulfonic acid is crystallized into chiral space group P212121. The 2A5NPH+ cation and anion are also alternately stacked with some dihedral angle to form column structures. These organic–organic cocrystals are controlled by the aromatic–aromatic interactions as well as multidirectional ionic and hydrogen bondings between the 2A5NPH+ cations and Ar–SO3 − anions. Second-harmonic generation (SHG) powers of the crystals measured by second-harmonic generation with evanescent wave (SHEW) technique were, however, smaller than that of urea. The reasons for small SHG powers are discussed based on the molecular arrangements.