Crystal Engineering of Noncentrosymmetric Structures Based on 2-Amino-5-nitropyridine and n-Chloroacetic Acid Assemblies

Abstract

New noncentrosymmetric crystals including the 2-amino-5-nitropyridinium and 2-amino-5-nitropyridine chromophores have been designed following a strategy first applied to the 2-amino-5-nitropyridinium dihydrogen phosphate. If a counteranion able to self-aggregate in chains or layers as (H 2 PO 4 -) n is associated to the 2-amino-5-nitropyridinium cation, a noncentrosymmetric structure based on herringbone motifs is systematically formed. In the same way it has been observed that a bulky group grafted on the amine radical of the 2-amino-5-nitropyridine induces a noncentrosymmetric structure containing herringbone motifs of molecular entities. The structures of the 2-amino-5-nitropyridinium dichloroacetate ionic crystal and 2-amino-5-nitropyridine/chloroacetic acid cocrystal having respectively the P2 1 2 1 2 1 and Cc symmetries confirm the validity of this strategy. The packings of these assemblies are discussed in terms of steric hindrance and hydrogen bonds. Powder samples of these materials exhibit second harmonic generation signals comparable to that of 3-methyl-4-nitropyridine N-oxide under Nd 3+ :YAG laser (1.06 µm) illumination.

Semiorganic Nonlinear Optical Material: Preparation and Properties of (NH4)·Sr[l-(+)-C4H2O6·B(OH)2]·4H2O

“…Because BO 4 tetrahedra are considered weak SHG originators, the NLO effect in SCB likely originates from tartrate groups. Furthermore, Nicoud et al have suggested that organic groups grafted on an inorganic framework are always associated with a NCS crystal structure. Additionally, the presence of delocalized π-electron systems, which enhance asymmetric polarizability, is the primary reason for the nonlinearity in organic materials, and such measurements also help to confirm the assignment of this structure in a NCS setting.…”

A Survey of Cocrystals Reported Prior to 2000

“…Knowing that 2-aminopyrimidine and, often, carboxylic acids exist as hydrogen-bonded dimers in their homomeric crystal structures, she reasoned that they might form heteromeric dimers which would be supramolecular heterosynthons for new structures (Figure ). That proved to be the case, leading to the discovery of new, 2-aminopyrimidine-containing cocrystals in her laboratories as well as by other research groups (Table ). − Similarly, carboxylic acids were found to form supramolecular heterosynthons with other functionalized heterocyclic bases such as 2-amino-5-nitropyridine and 2-pyridone . Cocrystals containing other hydrogen bonding patterns were constructed by similar analyses of homomeric structures, examples being the cocrystals containing 2-aminopyrimidones and dicarboxylic acids …”

Crystal Engineering: Strategies and Architectures

“…The use of similar building blocks in crystal engineering (notably in the design of non-linear optical materials) has received widespread attention and many groups are making important contributions to our understanding of exercising precise control over interplanar distances, layer topology and other structural features that eventually determine the physical properties of these materials (Zyss, Pecaut, Levy & Masse, 1993;Watanabe, Noritake, Hirose, Okada & Kurauchi, 1993;Kadirvelraj, Umarji, Robinson, Bhattacharaya & Guru Row, 1996;Bhattacharaya, Dastidar & Guru Row, 1994;Lefur, Bagieu-Beucher, Masse, Nicoud & Levy, 1996). Although these structures contain several predictable structural features, they do not represent materials over which we can claim complete control.…”