Solvent and Counteranion Assisted Dynamic Self-Assembly of Molecular Triangles and Tetrahedral Cages

Kumar, A and Banerjee, R and Zangrando, E and Mukherjee, PS (2021) Solvent and Counteranion Assisted Dynamic Self-Assembly of Molecular Triangles and Tetrahedral Cages. In: Inorganic Chemistry .

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Abstract

Self-assembly of naked PdII ions separately with newly designed bis(3-pyridyl)benzothiadiazole (L1) and bis(3-pyridyl)thiazolo5,4-dthiazole (L2) donors separately, under varying experimental conditions, yielded Pd4L8 (L= L1 or L2) tetrahedral cages and their homologous Pd3L6 (L= L1 or L2) double-walled triangular macrocycles. The resulting assemblies exhibited solvent, temperature, and counteranion induced dynamic equilibrium. Treatment of L1 with Pd(BF4)2 in acetonitrile (ACN) resulted in selective formation of a tetrahedral cage Pd4(L1)8(BF4)8 (1a), which is in dynamic equilibrium with its homologue triangle Pd3(L1)6(BF4)6 (2a) in dimethyl sulfoxide (DMSO). On the other hand, similar self-assembly using L2 instead of L1 yielded an equilibrium mixture of tetrahedral cage Pd4(L2)8(BF4)8 (3a) and triangle Pd3(L2)6(BF4)6 (4a) forms in both ACN and DMSO. The assembles were characterized by multinuclear NMR and ESI-MS while the structure of the tetrahedral cage (1a) was determined by single crystal X-ray diffraction. Existence of a dynamic equilibrium between the assemblies in solution has been investigated via variable temperature 1H NMR. The equilibrium constant K = (Pd4L83/Pd3L64) was calculated at each experimental temperature and fitted with the Van't Hoff equation to determine the standard enthalpy (�H°) and entropy (�S°) associated with the interconversion of the double-walled triangle to tetrahedral cage. The thermodynamic feasibility of structural interconversion was analyzed from the change in �G°, which suggests favorable conversion of Pd3L6 triangle to Pd4L8 cage at elevated temperature for L1 in DMSO and L2 in ACN. Interestingly, similar self-assembly reactions of L1 and L2 with Pd(NO3)2 instead of Pd(BF4)2 resulted in selective formation of a tetrahedral cage Pd4(L1)8(NO3)8 (1b) and double-walled triangle Pd3(L2)6(NO3)6 (4b), respectively. © 2022 American Chemical Society.

Item Type:	Journal Article
Publication:	Inorganic Chemistry
Publisher:	American Chemical Society
Additional Information:	The copyright for this article belongs to American Chemical Society
Department/Centre:	Division of Chemical Sciences > Inorganic & Physical Chemistry
Date Deposited:	13 Feb 2022 08:45
Last Modified:	13 Feb 2022 08:45
URI:	http://eprints.iisc.ac.in/id/eprint/71373

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