Equilibria between metallosupramolecular squares and triangles with the new rigid linker 1,4-bis(4-pyridyl)tetrafluorobenzene. Experimental and theoretical study of the structural dependence of NMR data

The new fluorinated rigid ligand L, 1,4-bis(4-pyridyl)tetrafluorobenzene, was used in combination with different diphosphine Pd(II) and Pt(II) triflates to build metallosupramolecular assemblies. Complex equilibria between triangular and square entities were detected for all the cases. Characterization of the equilibria was accomplished by H-1, P-31{H-1}, F-19, and Pt-195{H-1} NMR in combination with mass spectrometry. The square/triangle ratio was seen to depend on several factors, such as the nature of the metal corners, the concentration, and the solvent. The relative stability of the square and triangular complexes was explored by using force field methods. A GIAO-DFT study was carried out to analyze the changes of the P-31 and H-1 NMR data with the geometry of the complexes.