Rhenium(I) Block Copolymers Based on Polyvinylpyrrolidone: A Successful Strategy to Water-Solubility and Biocompatibility

A series of diphosphine Re(I) complexes Re1–Re4 have been designed via decoration of the archetypal core {Re(CO)2(N^N)} through the installations of the phosphines P0 and P1 bearing the terminal double bond, where N^N = 2,2′-bipyridine (N^N1), 4,4′-di-tert-butyl-2,2′-bipyridine (N^N2) or 2,9-dimethyl-1,10-phenanthroline (N^N3) and P0 = diphenylvinylphosphine, and P1 = 4-(diphenylphosphino)styrene. These complexes were copolymerized with the corresponding N-vinylpyrrolidone-based Macro-RAFT agents of different polymer chain lengths to give water-soluble copolymers of low-molecular p(VP-l-Re) and high-molecular p(VP-h-Re) block-copolymers containing rhenium complexes. Compounds Re1–Re4, as well as the copolymers p(VP-l-Re) and p(VP-h-Re), demonstrate phosphorescence from a 3MLCT excited state typical for this type of chromophores. The copolymers p(VP-l-Re#) and p(VP-h-Re#) display weak sensitivity to molecular oxygen in aqueous and buffered media, which becomes almost negligible in the model physiological media. In cell experiments with CHO-K1 cell line, p(VP-l-Re2) and p(VP-h-Re2) displayed significantly reduced toxicity compared to the initial Re2 complex and internalized into cells presumably by endocytic pathways, being eventually accumulated in endosomes. The sensitivity of the copolymers to oxygen examined in CHO-K1 cells via phosphorescence lifetime imaging microscopy (PLIM) proved to be inessential

Hybrid Inorganic-Organic Complexes of Zn, Cd, and Pb with a Cationic Phenanthro-diimine Ligand

Funding Information: Financial support from the Academy of Finland (decision 317903, I.O.K.; decision 340584, T.E. and A.J.K.; Flagship Programme, Photonics Research and Innovation PREIN, decision 320166) and computational resources from the Finnish IT Center for Science (CSC) are gratefully acknowledged. Publisher Copyright: © 2022 The Authors. Published by American Chemical Society.The phosphonium-decorated phenanthro-imidazolyl pyridine ligand, LP +Br, readily reacts with zinc(II) and cadmium(II) bromides to give inorganic-organic zero-dimensional compounds [ LP +ZnBr2]2[ZnBr4] ( 1 ) and [( LP +)2Cd2Br4][CdBr4] ( 2 ), respectively, upon crystallization. These salts are moderately fluorescent in the solid state under ambient conditions (λem = 458 nm, φem = 0.11 for 1 ; λem = 460 nm, φem = 0.13 for 2 ). Their emission results from spin-allowed electronic transitions localized on the organic component with the negligible effect of [MBr4]2- and MBr2 units. Contrary to ionic species 1 and 2 , lead(II) bromide affords a neutral and water-stable complex [( LP +)2Pb3Br8] ( 3 ), showing weak room-temperature phosphorescence arising from spin-orbit coupling due to the heavy atom effect. The emission, which is substantially enhanced for the amorphous sample of 3 (λem = 575 nm, φem = 0.06), is assigned to the intraligand triplet excited state, which is a rare phenomenon among Pb(II) molecular materials.Peer reviewe

Hybrid Inorganic–Organic Complexes of Zn, Cd, and Pb with a Cationic Phenanthro-diimine Ligand

The phosphonium-decorated phenanthro-imidazolyl pyridine ligand, LP+Br, readily reacts with zinc(II) and cadmium(II) bromides to give inorganic–organic zero-dimensional compounds [LP+ZnBr2]2[ZnBr4] (1) and [(LP+)2Cd2Br4][CdBr4] (2), respectively, upon crystallization. These salts are moderately fluorescent in the solid state under ambient conditions (λem = 458 nm, Φem = 0.11 for 1; λem = 460 nm, Φem = 0.13 for 2). Their emission results from spin-allowed electronic transitions localized on the organic component with the negligible effect of [MBr4]2– and MBr2 units. Contrary to ionic species 1 and 2, lead(II) bromide affords a neutral and water-stable complex [(LP+)2Pb3Br8] (3), showing weak room-temperature phosphorescence arising from spin–orbit coupling due to the heavy atom effect. The emission, which is substantially enhanced for the amorphous sample of 3 (λem = 575 nm, Φem = 0.06), is assigned to the intraligand triplet excited state, which is a rare phenomenon among Pb(II) molecular materials

Chromophore-Functionalized Phenanthro-diimine Ligands and Their Re(I) Complexes

A series of diimine ligands has been designed on the basis of 2-pyridyl-1<i>H</i>-phenanthro­[9,10-<i>d</i>]­imidazole (<b>L1</b>, <b>L2</b>). Coupling the basic motif of <b>L1</b> with anthracene-containing fragments affords the bichromophore compounds <b>L3</b>–<b>L5</b>, of which <b>L4</b> and <b>L5</b> adopt a donor–acceptor architecture. The latter allows intramolecular charge transfer with intense absorption bands in the visible spectrum (lowest λ_abs 464 nm (ε = 1.2 × 10⁴ M^–1 cm^–1) and 490 nm (ε = 5.2 × 10⁴ M^–1 cm^–1) in CH₂Cl₂ for <b>L4</b> and <b>L5</b>, respectively). <b>L1</b>–<b>L5</b> show strong fluorescence in a fluid medium (Φ_em = 22–92%, λ_em 370–602 nm in CH₂Cl₂); discernible emission solvatochromism is observed for <b>L4</b> and <b>L5</b>. In addition, the presence of pyridyl (<b>L1</b>–<b>L5</b>) and dimethylaminophenyl (<b>L5</b>) groups enables reversible alteration of their optical properties by means of protonation. Ligands <b>L1</b>–<b>L5</b> were used to synthesize the corresponding [Re­(CO)₃X­(diimine)] (X = Cl, <b>1</b>–<b>5</b>; X = CN, <b>1</b>-<b>CN</b>) complexes. <b>1</b> and <b>2</b> exhibit unusual dual emission of singlet and triplet parentage, which originate from independently populated ¹ππ* and ³MLCT excited states. In contrast to the majority of the reported Re­(I) carbonyl luminophores, complexes <b>3</b>–<b>5</b> display moderately intense ligand-based fluorescence from an anthracene-containing secondary chromophore and complete quenching of emission from the ³MLCT state presumably due to the triplet–triplet energy transfer (³MLCT → ³ILCT)