Diiminoisoindoline: tautomerism, conformations, and polymorphism

Abstract

Two polymorphs of the industrially important compound diiminoisoindoline occur in the amino tautomeric form as a conformational isomorph with a 1 : 1 mixture of the syn- and anti-isomers, and a conformational polymorph containing only the syn-isomer.

Platinum(II)‐Mediated Double Coupling of 2,3‐Diphenylmaleimidine with Nitrile Functionalities To Give Annulated Pentaazanonatetraenate (PANT) Systems

“…Such a tautomeric equilibrium was established for the related amidines, HN=C(R)-NHR′ # H 2 N-C(R)=NR′, by a series of chemical and physicochemical experiments, [40,41] and also for phthalimidine. [26] In accord with literature data, [42][43][44] the latter exists in tautomeric equilibrium between the amino and imino forms. Theoretical [43,44] and X-ray diffraction [42] studies indicate that the imino form possesses lower energy and is therefore expected to be the predominant in the solution, whereas the amino form is prevalent in the solid state because of the intermolecular hydrogen bond that is formed.…”

“…[26] In accord with literature data, [42][43][44] the latter exists in tautomeric equilibrium between the amino and imino forms. Theoretical [43,44] and X-ray diffraction [42] studies indicate that the imino form possesses lower energy and is therefore expected to be the predominant in the solution, whereas the amino form is prevalent in the solid state because of the intermolecular hydrogen bond that is formed. On the other hand, NMR spectroscopic studies [45] show that phthalimidine exists in [D 6 ]DMSO solution as a 5:1 mixture of the amino and imino forms.…”

[Cu(X-salicylato)2(N,N-diethylnicotinamide)2(H2O)2] complexes: conformational polymorphism and its consequence in supramolecular hydrogen-bonding networks formation

“…The monodentate bonding mode of the dena ligand is even more dominant for carboxylatocopper(II) complexes and there are two main stoichiometries within this group of complexes with the dena ligand. The 1:1 stoichiometry is found in paddle-wheel dinuclear complexes type [Cu 2 (RCOO) 4 (dena) 2 ] [12, [26][27][28]. The most frequent 1:2 stoichiometry can be found in monomeric complexes of Cu(RCOO) 2 (dena) 2 (H 2 O) x , where x = 0, [29,30], x = 2 [18,[31][32][33][34][35], or x = 4 [36], and in all those complexes the dena molecules are monodentate N donor ligands.…”

“…The most frequent 1:2 stoichiometry can be found in monomeric complexes of Cu(RCOO) 2 (dena) 2 (H 2 O) x , where x = 0, [29,30], x = 2 [18,[31][32][33][34][35], or x = 4 [36], and in all those complexes the dena molecules are monodentate N donor ligands. Recently, the first two polymeric complexes with bridging dena molecules, of the composition [Cu 2 (RCOO) 4 (dena) 1 ] n , have been structurally characterized [17,18].…”

“…Various forms of polymorphism, including concomitant [2], packing [3], and conformational [4] have been studied as interesting phenomena in the solid-state sciences. The development of novel polymorphs of potential and existing drugs has for some time been a method for modifying and improving their physical properties [5].…”