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We present several multicomponent crystalline species formed by zwitterionic GABA analogues pregabalin and phenibut. These compounds are evaluated based on their crystal structure in congruence with properties such as melting behaviour, solubility, and lattice energies. Furthermore, it is discussed how major property distinctions between a homo- and heterochiral co-crystalline system enable enantiopurification of pregabalin. [ABSTRACT FROM AUTHOR]

The Schiff-base ligand N-2-(pyridyl)salicylaldimine (HL) reacts with zinc(ii) acetate or nitrate to obtain the enantiomorphous chiral-at-metal compound Δ/Λ-bis[N-2-(pyridyl)salicylaldiminato-κ2N,O]zinc(ii), [Zn(L)2] (1), which crystallizes as a racemic conglomerate via spontaneous resolution. Two deprotonated N,O-chelate ligands form a pseudo-tetrahedral N2O2-coordination sphere with a Δ/Λ-configured zinc atom. The Δ- and Λ-configured molecular complexes in 1 assemble in P (right)- and M (left)-handed 41- and 43-helical chains in the chiral space groups P41212 and P43212, respectively, through weak C–H…O hydrogen bonding between neighbouring molecules along the chain axis. Only molecules of the same Δ- or Λ-configuration combine into a helical chain and only chains of the same P- or M-handedness combine to form homochiral crystals. According to the analyses of intermolecular interactions with the Hirshfeld surface, the supramolecular packing features C–H…O bonding as the most apparent significant contribution. This is a rare example of solely weak C–H…O hydrogen bonding interaction leading to spontaneous resolution to a racemic conglomerate. This case also supports the notion of less repulsive packing interactions between homochiral molecules because of spin polarization. Optimized structures and excited state properties by DFT/TD-DFT calculations are comparable to experimental results. [ABSTRACT FROM AUTHOR]

The ditopic ligands 3,5-dimethyl-pyrazolate-4-carboxylate, –Me2pzCO2–, and 4-(3,5-dimethyl-1H-pyrazol-4-yl)benzoate, –Me2pzC6H4CO2–, combine a pyrazolate and carboxylate functionality in axial orientation and lead to porous cobalt or zinc azolate–carboxylate frameworks that have the same cubic pcu-a topology and {M4(μ4-O)} nodes (M = Co, Zn) as MOF-5 and other IRMOFs. The microporous networks [M4(μ4-O)(Me2pzCO2)3] (M = Co, Zn) with the short linker exhibit a solvent-induced gate effect, evidenced by gas desorption hysteresis due to small pore apertures of 2.8 Å diameter together with small amounts of high-boiling solvent remaining in the activated samples. For [Co4(μ4-O)(Me2pzCO2)3], the low-pressure H2 storage capacity (1.7 wt%, 1 bar , 77 K) is higher than for MOF-5, and the CO2 uptake of 20.8 wt% puts it among the top MOFs for low-pressure CO2 sorption even though the BET surface is less than 1000 m2 g−1. The analysis of the magnetic properties of [Co4(μ4-O)(Me2pzCO2)3] takes into account the distribution of tetrahedra resulting from the disorder of the pyrazolate–carboxylate linker. An antiferromagnetic coupling observed for [Co4(μ4-O)(Me2pzCO2)3] arises from the interactions of the cobalt(ii) ions through the combined μ4-O + syn–syn carboxylate and μ4-O + pyrazolate bridges. [ABSTRACT FROM AUTHOR]