P. Bombicz, IUCrJ (2024) 11, 1-2
The phenomenon and definition of isostructurality are discussed. It deserves reconsideration regarding the aspects of symmetry, measure of similarity and formation of supramolecular interactions.
Investigation of isostructurality leads to a deeper understanding of closepackingprinciplesandcontributestotheabilityofcrystalengineering.Agiven packingmotifmay tolerate small molecular changes within a limit. Slight alterationsofacrystalpackingarrangementarecarriedoutinordertofine-tune thestructural andmacroscopicproperties, keepingthebalanceof thespatial requirementsandelectrostaticeffectsof thealteredmolecules inthecrystals, preservingtheirisostructurality.Evenso,thedefinitionofisostructuralityisnot explicitaboutseveral issues.Arethecorrespondingstructuresrequiredtohave the same stoichiometry, Z0, symmetryelements and the same spacegroup? Because it isnotobvious inthedefinition, studiesonstructureanalysisand softwarecalculatingvariousnumericaldescriptorsdevelopedforthequantitativecomparisonof thedegreeof similarityof isostructural crystalsself-define their criteria. The extent of the difference between corresponding crystal structures referredtoas isostructural isnot limited. Shoulditbedetermined numerically?There is nothing in thedefinitionabout ademand for similar supramoleculararrangements inisostructural crystals.Shouldthesimilarityof supramolecularinteractionsbeacriterionof isostructurality?Thedefinitionof isostructurality deserves reconsideration regarding symmetry, measure of similarityandformationofsupramolecular interactions.