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.

Five manganese(i) tricarbonyl complexes of the general formulae [Mn(bpea(N=CHC6H4R))(CO)3]PF6 and [Mn(bpea(NHCH2C6H4R))(CO)3]PF6 based on the tridentate bis(pyrazolyl)ethylamine (bpea) ligand, each containing a pendant 4-substituted phenyl group with R = H, I, and C≡C-H, were synthesized and fully characterized, including X-ray structure analysis for three compounds. All complexes are stable in the dark in aqueous buffer for an extended period of time. However, CO-release could be triggered by illumination at 365 nm, establishing these compounds as novel photoactivatable CO-releasing molecules (PhotoCORMs). The influence of the imine vs. amine group in the ligands on the electronic structure and the photophysical behavior was investigated with the aid of DFT and TDDFT calculations. Solution IR studies on selected compounds allowed identification of intermediates resulting from the photoreaction. Finally, light-induced CO release from a model compound was demonstrated both in PBS buffer and in vitro in human umbilical vein endothelial cells (HUVECs) using COP-1 as a fluorescent switch-on probe.

We present the optical, electrochemical, and electrochromic properties of Fe(ii)-, Co(ii)- and Ru(ii)-based metallo-supramolecular polymers (MEPEs) self-assembled from rigid, π-conjugated bis-terpyridines with different numbers of pyridine linkers.

The structure and properties of metallo-supramolecular polyelectrolytes (MEPEs) self-assembled from rigid 2,6-bis(2-pyridyl)pyrimidine and the metal ions Fe and Co are presented. While FeL1-MEPE (L1 = 1,4-bis[2,6-bis(2-pyridyl)pyrimidin-4-yl]benzene) is deep blue, FeL2- and CoL2-MEPE (L2 = 5,5'-bis[2,6-bis(2-pyridyl)pyrimidin-4-yl]-2,2'-bithiophene) are intense green and red in color, respectively. These novel MEPEs display a high extinction coefficient and solvatochromism. Ligand L2 shows a high absolute fluorescence quantum yield (Φ = 82%). Viscosity and static light-scattering measurements reveal that the molar masses of these MEPEs are in the range of 1 × 10 g/mol under the current experimental conditions. In water, FeL1-MEPE forms a viscous gel at 20 °C (c = 8 mM). Thin films of high optical quality are fabricated by dip coating on transparent conducting indium tin oxide (ITO) glass substrate. Optical, electrochemical, and electrochromic properties of the obtained MEPEs are presented. Green to red and blue to colorless electrochromism is observed for FeL2-MEPE and FeL1-MEPE, respectively. The results show that the electrochromic properties are affected by the ligand topology. The Fe-MEPEs show a reversible redox behavior of the Fe/Fe couple at 0.86 and 0.82 V versus Fc/Fc and display an excellent redox cycle stability under switching conditions. FeL2-MEPE in its oxidized state exhibits a broad absorption band covering the near-IR region (ca. 1500 nm) due to the ligand-to-metal charge transfer transition originating due to charge delocalization in the bithiophene spacer.

In this work, facial tricarbonylmanganese(I) complexes [Mn(bpea CH2C6H4R )(CO) 3 ]PF 6 incorporating a functionalized 2,2-bis(pyrazolyl)ethylamine (bpea) ligand with R = I, CϵCH, and CHO have been explored for their utility in bioorthogonal coupling to carrier peptides bearing N-terminal alkyne, azide, and aminoxy residues. As a model system, the transforming growth factor β-recognizing (TGF-β) peptide sequence RЈ-Leu-Pro-Leu-Gly-Asn-Ser-His-OH was used in which RЈ is the reactive group complementary to the metal complex functionality. The use of catalyst-free oxime ligation [a]