Abstract: While (macro)cyclic amines are widely used as co-formers in the design of supramolecular hydrogen-bonded crystalline networks, organic hydroxylamines remain almost unexplored in this context. Here, co-crystallization of the tetra-N-hydroxylated cyclam with several organic hydrogen-bond donors (pharmaceutically relevant carboxylic acids, hydroquinone) was investigated for the first time. The results demonstrate co-former-dependent control over crystal packing, proton transfer, supramolecular organization, macrocyclic conformation, and tautomerization leading to either closed H-bonded subunits or novel three-dimensional self-catenated H-bonded networks. In specific cases, the dynamic nature of crystal formation gives rise to conformational polymorphs. Remarkably, a very rare tautomerization of the hydroxylamine unit to the N-oxide form was observed in the co-crystal of cyclam(OH)4 with hydroquinone. Comparison of the observed H-bonding parameters and patterns with those of the known co-crystals of unsubstituted cyclam highlights the pronounced advantage of the hydroxylated scaffold in engineering supramolecular hydrogen-bonded motifs.

Cite: Lesnikov V.K. , Sukhorukov A.Y.
Cyclam(OH)₄ as an adaptable co-former for co-crystals with carboxylic acids and phenols
CrystEngComm. 2026. DOI: 10.1039/d6ce00350h WOS Scopus OpenAlex

Dates:

Submitted:	Apr 29, 2026
Accepted:	Jun 18, 2026
Published print:	Jun 18, 2026

Identifiers:

≡ Web of science:	WOS:001811491200001
≡ Scopus:	2-s2.0-105043819111
≡ OpenAlex:	W7165139736

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