Balancing supramolecular reagents for reliable formation of co-crystals

Abstract

The more than 365,000 organic and organometallic small-molecule crystal structures in the Cambridge Structural Database (CSD) are a good source of data for understanding the crystal structures of solvates. It is trivial with the existing search software [1] to find all CSD entries containing a particular solvent, say water, and a survey of the 50 most common solvents in the CSD has been published [2]. It might be interesting, however, to know if any of these solvates also exist in an unsolvated form; given a crystal structure of di-isopropylammonium chloride hydrate in the CSD, for example, one could wonder if a crystal structure of di-isopropylammonium chloride itself is present in the database. A computer program was written that for a given solvent molecule finds all pairs of solvated versus unsolvated CSD entries; a list of solvate structures for which no unsolvated form exists in the CSD is also generated. These lists enable us to examine if properties such as the number of hydrogen-bond donors / acceptors or the molecular flexibility influence solvate formation. Results for hydrates will be presented. [1] Bruno, I.J.; Cole, J.C.; Edgington, P.R.; Kessler, M.; Macrae, C.F.; McCabe, P.; Pearson, J.; Taylor, R.

Cocrystals of Kemp’s triacid. Part III: Structure of hydrogen-bonded complex of Kemp’s triacid with 1,1,3,3-tetramethylguanidine studied by X-ray and FT-IR methods

“…KTA C(1)AC (7) 1.546(2) C(3)AC (8) 1.519(2) C(5)AC (9) 1.545(2) C(7)AO (1) 1.199(3) C(7)AO (2) 1.328(2) C(8)AO (3) 1.1991(18) C(8)AO (4) 1.3090(18) C(9)AO (6) 1.2536(18) C(9)AO (5) 1.2596(18) C(2)AC(1)AC (7) 111.74(14) C(6)AC(1)AC (7) 117.19(14) C(7)AC(1)AC (10) 101.96(13) C(8)AC(3)AC (4) 108.94(13) C(8)AC(3)AC (11) 110.93(14) C(8)AC(3)AC (2) 109.89(12) C(4)AC(5)AC (9) 113.07(12) C(6)AC(5)AC (9) 114.20(12) C(9)AC(5)AC (12) 103.69(13) O(1)AC (7)AO (2) 119.89 (17) TMG cation becomes chemically C 2 symmetric with respect to the pseudo C 2 axis along the C@N bond (Fig. 3).…”

“…Cocrystals are crystalline adducts between two molecules which are bonded to each other by hydrogen bonds of various strength [1][2][3][4][5]. A large number of cocrystals have been prepared using acids, especially di-or tri-carboxylic acids, which act as proton-donors in hydrogen-bonded systems and as linkers in supramolecular crystals [6][7][8][9][10][11][12].…”

Synthesis and crystal structures of two polymorphs of sulfathiazole:pyridine (1:1) adducts

“…Nitrogen atoms of the amino-, pyridine-, aniline-fragments are very often used for this purpose [16][17][18]. Comparison of the crystal structures of the sulfathiazole:pyridine adducts with the structures of pure sulfathiazole polymorphs can also illustrate the role of relative proton-donor/proton-acceptor ability in crystal structure formation.…”

Searching the Cambridge Structural Database for solvatedvsunsolvated pairs

“…Since the odds are stacked firmly in favor of a homomeric product, how do we go about developing reliable and versatile synthetic methods for the directed assembly of co-crystals? This presentation will attempt to answer the question by outlining several modular hydrogen-bond driven strategies for the design and synthesis of binary and ternary supermolecules and co-crystals [1][2][3].…”