ORIGINAL RESEARCH N-H…O, C-H… O hydrogen-bonded supramolecular frameworks in 4-fluoroanilinium and dicyclohexylaminium picrate salts Saminathan Kolandaivelu 1 & Jagan Rajamoni 2 & Sivakumar Kandasamy 2 Received: 28 October 2019 /Accepted: 3 December 2019 # Springer Science+Business Media, LLC, part of Springer Nature 2019 Abstract The asymmetric unit of compound (I), 4-fluoroanilinium picrate, C 6 H 7 NF + .C 6 H 2 N 3 O 7 - contain one 4-fluoroanilinium cation and one picrate anion whereas in compound (II), dicyclohexylaminium picrate, C 12 H 22 N + .C 6 H 2 N 3 O 7 - the asymmetric unit contains two sets of dicyclohexylaminium cation and picrate anion due to conformational difference between the molecules. In (I), all three nitro groups of the picrate anion are positionally disordered over two sites refined to major and minor components. The molecular ions of (I), interlinked through N–H O and C–H O hydrogen bonds forming two-dimensional supramolecular sheet along (-1 0 1) plane. Whereas in (II), the symmetry-independent molecules labeled as A and B molecule form independent one-dimensional supramolecular tape extending along (1 1 0) and (1 0 0) direction. The supramolecular tapes are interlinked through C–H O interaction to form three-dimensional network in the crystalline solid in (II). Keywords Supramolecular . Hydrogen bond . Picrate . Framework . FT-IR . Motif Introduction Crystal engineering of organic solids, especially with re- spect to understanding the nature of various intermolecular interactions, have profoundly influenced the concept of supramolecular chemistry [1, 2]. The nature of intermolec- ular interactions influences crystal engineering including hydrogen bond, weak interaction, halogen bond, π…π in- teraction, and short contacts between molecular or ionic compounds [3]. The specificity, directionality, and predict- ability of intermolecular interaction/hydrogen bond can be utilized to assemble supramolecular structures with con- trolled dimensionality which tend to exhibit interesting electrical, magnetic, and optical properties of our interest [4, 5]. Among all non-covalent interactions, hydrogen bond plays an important role in chemistry, biology, and materials science. Identifying hydrogen-bonded motifs and supramolecular synthons are very important to crystal engineering as hydrogen bonded motifs between building blocks that can be used to propagate networks or supramo- lecular structures [6, 7]. Formation of salts and co-crystals favors the understanding of supramolecular synthon which enables us to enhance the desired properties. Picric acid forms crystalline co-crystals and salts with various organic molecules by virtue of its acidic nature and forms salts through specific electrostatic and hydrogen bonding inter- actions. Picric acid (2,4,6 trinitrophenol) is an organic acid which is used in dyeing industry and explosive. Picric acid is used in human therapy as treating burns, antiseptic, and astringent agent [8]. The presence of electron-withdrawing groups makes it as a π-acceptor for a neutral carrier donor molecule. A variety of picrate salts have been previously reported by us and others such as piperidinium picrate, 3- methylanilinium picrate, l-prolinium picrate, and 2-amino 4,6 dimethoxypyrimidinium picrate [9–12]. It is observed that picrate salts form interesting hydrogen-bonded supra- molecular motifs and one-, two-, and three-dimensional networks with respect to the nature of the substitution pres- ent in cations. Reported literature shows that bulk crystals of picrate salts are best candidates which exhibit good non- linear optical properties [13, 14]. In the present work, we have studied the crystal structure and hydrogen-bonded supramolecular networks in 4-fluoroanilinium picrate and dicyclohexylamminium picrate salts as follows. * Jagan Rajamoni phyjagan@gmail.com 1 Department of Physics, University V.O.C.College of Engineering, Anna University, Tuticorin 628008, India 2 Department of Physics, Anna University, Chennai 600 025, India Structural Chemistry https://doi.org/10.1007/s11224-019-01471-1