Crystal Packing Diversity in Azo-Labeled Amino Acid Esters: Structural Origins of Z′ Variability

Bjelopetrović, Alen; Morasi Piperčić, Sara; Juribašić Kulcsar, Marina (2026) Crystal Packing Diversity in Azo-Labeled Amino Acid Esters: Structural Origins of Z′ Variability. Crystal Growth and Design . ISSN 1528-7505

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Abstract

Nine mechanochemically prepared 4′-(N,N-dimethylamino)azobenzene-n-carboxamides (n = 2–4) derived from α-amino acid esters were structurally characterized. X-ray diffraction on single crystals of chiral amides reveals a notably high incidence of structures with Z′ > 1 (five out of eight). Structural analysis indicates that this behavior arises from a combination of synthon frustration, conformational flexibility, and competing intermolecular interactions. Hirshfeld surface and interaction energy analyses show that crystal packing is predominantly governed by dispersion forces, while hydrogen bonding provides directional organization. Comparative packing analysis including identification of the isostructural pairs across the ortho-, meta-, and para-series demonstrate that both azobenzene moiety and amino acid side chain modulate packing motifs. Pseudosymmetry analysis confirms that the observed high-Z′ packing is a consequence of molecular chirality, conformational variability, and diverse interaction patterns. Complementary Cambridge Structural Database analysis supports an above-average propensity for high-Z′ structures in α-amino acid ester amides, with derivatives of Glu methyl ester, Trp, and Phe showing a particularly increased likelihood of high-Z′ packing.

Item Type:	Article
Uncontrolled Keywords:	Amide; Amino Acid; Azobenzene; High Z’; Hirshfeld analysis
Subjects:	NATURAL SCIENCES > Chemistry
Divisions:	Division of Materials Chemistry
Projects:	Project title Project leader Project code Project type Zelena sinteza organopaladijevih foto-osjetljivih spojeva-GREENSENS Manda Ćurić IP-2014-09-7984 HRZZ Mehanokemijska aktivacija i funkcionalizacija veze C–H potaknuta paladijem i usmjerena ligandom-MECHEMFUN Manda Ćurić IP-2019-04-9951 HRZZ Mehanokemijske reakcije boronskih kiselina s aminima i karbonilnim spojevima praćene in situ Ramanovom spektroskopijom Marina Juribašić Kulcsar IP-2025-02-3843 HRZZ Reakcije boronskih kiselina i njihovih derivata u čvrstom stanju Marina Juribašić Kulcsar KP1-01-917/1-2025 IRB NPOO
Depositing User:	Marina Juribašić Kulcsar
Date Deposited:	06 Oct 2026 07:22
URI:	https://fulir.irb.hr:/id/eprint/12142
DOI:	10.1021/acs.cgd.6c00256

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