Next Generation PhotoCORMs: Polynuclear Tricarbonylmanganese(I)-Functionalized Polypyridyl Metallodendrimers

Abstract

The first CO-releasing metallodendrimers, based on polypyridyl dendritic scaffolds functionalized with Mn(CO)3 moieties, of the general formula [DAB-PPI-{MnBr(bpy(CH3,CH═N))(CO)3}n], where DAB = 1,4-diaminobutane, PPI = poly(propyleneimine), bpy = bipyridyl, and n = 4 for first- or n = 8 for second-generation dendrimers, were synthesized and comprehensively characterized by analytical (HR-ESI mass spectrometry and elemental analysis) and spectroscopic ((1)H, (13)C{(1)H}-NMR, infrared, and UV/vis spectroscopy) methods. The CO-release properties of these compounds were investigated in pure buffer and using the myoglobin assay. Both metallodendrimer generations are stable in the dark in aqueous buffer for up to 16 h but show photoactivated CO release upon excitation at 410 nm, representing a novel class of macromolecular photoactivatable CO-releasing molecules (PhotoCORMs). No scaling effects were observed since both metallodendrimers release ∼65% of the total number of CO ligands per molecule, regardless of the generation number. In addition, the mononuclear model complex [MnBr(bpy(CH3,CH═NCH2CH2CH3))(CO)3] was prepared and comprehensively studied, including DFT/TDDFT calculations. These metallodendrimer-based PhotoCORMs afford new methods of targeted delivery of large amounts of carbon monoxide to cellular systems.

Carbon monoxide – physiology, detection and controlled release

“…Thus, a metallodendritic photoCORM was built from an organic dendrimer with 2,2′-bipyridyl end groups acting as strong bidentate ligands to multiple Mn(CO) 4 fragments. 144 …”

PhotoCORMs: CO release moves into the visible

“…Smith and co-workers have exploited the bypyridyl ligand bound to manganese to develop dendritic photoCORMs. 68 These systems were prepared in two dendrimer generations, bearing four and eight metal centres, respectively. Both showed stability in the dark with CO release at 410 nm and comparable total CO quantities available.…”

Light responsive metal–organic frameworks as controllable CO-releasing cell culture substrates

“…12 In addition, the payload of CO in photoCORMAs is higher than in their molecular counterparts, and the extent of leached by-products is limited because the metal carbonyl moiety is immobilized in the scaffold. Thus, to date, photoCORMs have been assembled into dendritic structures, 13 covalently immobilized onto the surfaces of nanoparticles, 14–16 protein cages, 17 or organic polymers, 18 trapped in polymer fibers, 19 and mesoporous silica. 20 …”