@article {154,
	title = {When does a supramolecular synthon fail? Comparison of bridgehead-functionalized adamantanes: the tri- and tetra- amides and amine hydrochlorides},
	journal = {Crystal Growth \& Design},
	year = {2019},
	month = {July 12, 2019},
	type = {Full paper},
	abstract = {<p>1,3,5-trisubstituted adamantane carboxamide and amine hydrochloride, Ad(CONH2)3 {\textperiodcentered} 2.5H2O and [Ad(NH3)3]Cl3 {\textperiodcentered} H2O (Ad = adamant-n-yl) respectively, crystallized from aqueous solutions, possess crystal structures with predictable H-bonded assembly, consistent with the C3v symmetry of the building blocks. The triamide structure consists of interpenetrated hexagonal networks, sustained by the well-known cyclic H-bonded bis-amide synthon, R22(8), which ensures linear connectivity. The structure of the triamine hydrochloride, assembled through the tetrahedral {RN+H3---(Cl-)3} synthon, features a remarkably symmetric assembly with narrow trigonal pore-channels, hosting water molecules. The structures of the tetrahedral 1,3,5,7-tetrasubstituted Ad(CONH2)4 and [Ad(NH3)4]Cl4, obtained similarly, demonstrate a formal prediction failure of synthon based approach. Instead of the anticipated bis-amide synthon based diamond network (1.485 g cm-3) analogous to the 5-fold interpenetrated paradigmatic structure of Ad(COOH)4, a non-interpenetrated assembly, sustained by a dense network of H-bonds, is realized (1.433 g cm-3). Lessened geometric regularity was also found in the tetrahydrochloride salt assembled via 5-connected nodes, {RN+H3---(Cl-)4}, which involve a bifurcated H-bond. The failures of the supramolecular synthons in these simple cases could be interpreted either in terms of symmetry and/or limitations associated with the {\textquoteleft}synthon-density{\textquoteright}. A potential machine learning approach oriented on heuristic retrosupramolecular synthesis relies on such selected high-weight conceptual cases.</p>},
	keywords = {adamantane, amide, amine, crystal structure, H-bond, hydrochloride, prediction, supramolecular synthon, violation},
	doi = {https://doi.org/10.1021/acs.cgd.9b00594},
	url = {https://pubs.acs.org/doi/10.1021/acs.cgd.9b00594},
	author = {Ishtvan Boldog and Guido Reiss and Kostiantyn V. Domasevitch and Tomas Base and Stefan Braese}
}
