Search

The ability to predict and control the assembly of molecular and ionic species into ordered networks is becoming an important target area in chemistry, biochemistry and materials science. In this context, the selectivity and directionality of the hydrogen bond have been instrumental in the preparation of distinctive structural aggregates, and the use of hydrogen bonding as a steering force is now emerging as the most important strategy in crystal engineering. A reliable supramolecular synthetic protocol also requires access to a wide range of reactions that are versatile, selective and give rise to high supramolecular yields. Through a systematic structural study we have examined three issues that are relevant to the development of transferable supramolecular synthesis; (a) structural invariance to molecular isomerism; (b) hierarchy of synthons based upon competition between intermolecular forces and (c) changes in supramolecular yield as a function of molecular substitution.

The notion that the best hydrogen-bond donor preferentially interacts with the best hydrogen-bond acceptor has been explored in the synthesis and structural characterization of 12 salts based on asymmetric 2-aminopyrimidinium cations: 2-amino-4-methoxy-6-methylpyrimidinium 2-fluorobenzoate, 2-amino-4-methoxy-6-methylpyrimidinium 3-chlorobenzoate, 2-amino-4-methoxy-6-methylpyrimidinium 3-nitrobenzoate, 2-amino-4-methoxy-6-methylpyrimidinium benzoate, 2-amino-4-methoxy-6-methylpyrimidinium 3-N,N ‘(dimethyl)aminobenzoate, 2-amino-4-methoxy-6-methylpyrimidinium methylene-hydrogensuccinate hydrate, bis(2-amino-4-methylpyrimidinium) fumarate, 2-amino-4-methylpyrimidinium 3-fluorobenzoate, 2-amino-4-methylpyrimidinium nitrate, 2-amino-4-methylpyrimidinium 3-chlorobenzoate, 2-amino-4-methylpyrimidinium 2-methyl-hydrogenmaleate, and 2-amino-4-chloro-6-methylpyrimidinium 3,5-dinitrobenzoate toluene0.4. In each structure, the −COO- acceptor consistently seeks out the −N−H+ donor generating the most important interm...

Tetracyanocalix[4]arene has been synthesized in a cone conformation and crystallized from solution in an orthorhombic system, space group P212121, with a = 13.7999(9) A, b = 16.820(1) A, c = 21.754(1) A, Dc = 1.218 g/cm3, Z = 4 (C62H47N5O4). Refinement based on 11008 observed reflections yielded R1 = 0.042. Further crystallographic studies have revealed that this compound self-assembles into a one-dimensional coordination polymer in the presence of Ag+ cation. This extended structure also crystallizes in an orthorhombic system, space group Cmca, with a = 17.770(1) A, b = 31.498(2) A, c = 23.107(2) A, Dc = 1.319 g/cm3, Z = 8 (C63H52AgCl2F6N4O6P). Refinement based on 7391 observed reflections yielded R1 = 0.109.