The use of electrospray ionization tandem mass spectrometry on the structural characterization of novel asymmetric metallo-organic supermolecules, based on pentafluorophenylporphyrins and ruthenium complexes

Abstract

The novel asymmetric metallo-organic triads cis- and trans-[B(4-py)BPFPH 2{Ru 3O(Ac) 6(py) 2}{Ru(bpy) 2Cl}](PF 6) 2 ( 5a,b) for which cis- and trans-B(4-py)BPFPH 2 = 5,10-bis(pentafluorophenyl)-15,20-bis(4-pyridyl)porphyrin and 5,15-bis(pentafluorophenyl)-10,20-bis(4-pyridyl)porphyrin, respectively; Ac = acetate; py = pyridine and bpy = 2,2′-bipyridine, as well as their corresponding monosubstituted dyads cis- and trans-[B(4-py)BPFPH 2{Ru 3O(Ac) 6(py) 2}]PF 6 ( 4a,b) have been structurally characterized via electrospray ionization mass spectrometry (ESI-MS and ESI-MS/MS). The ESI-MS of dyads 4a,b display two characteristic Ru-multicomponent clusters of isotopologue ions corresponding to singly charged ions 4a,b + of m/ z 1629 and doubly charged ions [ 4a,b+H] 2+ of m/ z 815 and the triads 5a,b are detected by ESI-MS as the intact doubly charged cluster of isotopologue ions of m/ z 1039 [ 5a,b] 2+. The ESI-MS/MS of 4a,b +, [ 4a,b+H] 2+ and [ 5a,b] 2+ reveal characteristic dissociation pathways, which confirm the structural assignments providing additional information on the intrinsic binding strengths of the gaseous ions. Although the gas-phase behavior of each pair of isomers was rather similar, the less symmetric dyads 4a,b are distinguished via the 1H NMR spectral profile of the pyrrolic signals. Exploratory photophysical assays have shown that both modifying motifs alter the porphyrinic core emission profile, opening the possibility to use these asymmetric systems as photophysical devices.