Intriguing Case ofPseudo-Isomorphism between Chiral and Racemic Crystals of rac- and (S)/(R)2-(1,8-Naphthalimido)-2-quinuclidin-3-yl, and Their Reactivity Toward I₂and IBr

Abstract

Condensation reactions between 1,8-naphthalic anhydride and racemic 3-aminoquinuclidine or chiral (S) or (R)-(−)-3aminoquinuclidine allowed preparation of three novel racemic and enantiopure aza-donor ligands, namely NMiABCO (1), (S)NMiABCO (2a), and (R)NMiABCO (2b). Racemic NMiABCO (1) crystallizes in the monoclinic space group P2 1 /c, Z′ = 1, while enantiopure (S)NMiABCO (2a) and (R)NMiABCO (2b) crystallize in the chiral monoclinic space group P2 1 , Z′ = 2, and show significant pseudocentrosymmetry, being pseudo-isomorphous with racemic NMiABCO (1). Reactivity of both racemic and enantiopure NMiABCO toward iodine and interhalogen IBr was also investigated as a way to remove the pseudoisomorphism, yielding the three new molecular adducts [NMiABCO•I 2 ] (3), [(S)NMiABCO•I 2 ]•xCHCl 3 (4), [(S)NMiABCO•IBr]•xCHCl 3 (5) and the molecular salt [HNMiABCO][IBr 2 ] (6). Synthesis of complexes 3 and 4 was also carried out in the solid state via kneading and vapor digestion techniques. All compounds were fully characterized via single crystal and powder X-ray diffraction and Raman spectroscopy.

Reaction of Copper Halides with Dafone and Halogens – Magnetic Exchange in Dibromine Linked Chains of Cu(dafone)2X2

“…The IBr 2 – anion is nearly linear and unsymmetrical (2.667 Å, 2.700 Å, 177.7°). According to the CCDC data base, 74 crystal structures are reported for this ion with bond lengths in the range 2.6–2.7 Å, some of which are nearly symmetrical. The polybromide anionic chain in compound 4 (Figure ) is formed by linking Br 3 – ions and Br 2 molecules (Br–Br, 2.55 Å, Br ··· Br, 3.15 Å).…”

Solvent Effect on the Preparation of Ionic Cocrystals of dl-Amino Acids with Lithium Chloride: Conglomerate versus Racemate Formation

“…The ICCs l -Val·LiCl·H 2 O form II and racemate dl -Val·LiCl·H 2 O, i.e., the final, stable forms obtained upon leaving at ambient conditions for a few minutes the first products of the ball milling with MeOH, were recrystallized from water, and single crystals suitable for X-ray structural characterization could be grown. The two ICCs are quasi-isomorphous , (see Table SI-2); they crystallize in the monoclinic P 2 1 and P 2 1 / n space groups, respectively, and are characterized by the presence of infinite chains analogous to those present in l -Ala·LiCl·H 2 O form II (see Figure and Figure ).…”

“…The ICCs L-Val•LiCl•H 2 O form II and racemate DL-Val•LiCl• H 2 O, i.e., the final, stable forms obtained upon leaving at ambient conditions for a few minutes the first products of the ball milling with MeOH, were recrystallized from water, and single crystals suitable for X-ray structural characterization could be grown. The two ICCs are quasi-isomorphous53,54…”

Designing Solid Solutions of Enantiomers: Lack of Enantioselectivity of Chiral Naphthalimide Derivatives in the Solid State

“…Requirement for such structures therefore is that two (or other even number) of single enantiomer molecules in the asymmetric unit are approximate mirror images to each other. The study of 1 13 has shown that all the structural prerequisites for solid solution existence are present; furthermore, the racemic structure is isostructural with the enantiopure one (see Figure 2). Previously reported cases 5,7,21−23 of solid solutions show that molecules possessing relatively large conformational freedom around the chiral center are able to form quasi-centrosymmetric pairs.…”