Dendron-functionalized bis(terpyridine)-iron(II) or -cadmium(II) metallomacrocycles: Synthesis, traveling-wave ion-mobility mass spectrometry, and photophysical properties

The synthesis, purification, structural analysis, and photophysical properties of a series of five-, six-, and seven-sided Fe^II macrocycles and the corresponding hexameric Cd^II macrocycle, all prepared by self-assembly of a 120° bis(terpyridine) ligand modified with first- and second-generation 1→3 C-branched dendrons, are reported. All metallomacrocycles were fully characterized by ¹H and ¹³CNMR spectroscopy, traveling-wave ion-mobility mass spectrometry (TWIM MS), molecular modeling, UV/Vis absorption spectroscopy, photoluminescence, and cyclic voltammetry. A gradual increase of the collision cross sections of the Fe^II metallomacrocycles was observed with a successive increase of the number and molecular size of the ligands. The combination of ion-mobility mass spectrometry and NMR techniques unveils structural features that agree well with calculations. Extinction coefficients and emission are significantly modulated by increasing the ring size and changing the metal ion center from Fe^II to Cd^II.