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Lam TL, Tong KC, Yang C, Kwong WL, Guan X, Li MD, Kar-Yan Lo V, Lai-Fung Chan S, Lee Phillips D, Lok CN, Che CM. Luminescent ruffled iridium(iii) porphyrin complexes containing N-heterocyclic carbene ligands: structures, spectroscopies and potent antitumor activities under dark and light irradiation conditions. Chem Sci 2018; 10:293-309. [PMID: 30746082 PMCID: PMC6335621 DOI: 10.1039/c8sc02920b] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2018] [Accepted: 09/27/2018] [Indexed: 01/01/2023] Open
Abstract
A panel of iridium(iii) porphyrin complexes containing axial N-heterocyclic carbene (NHC) ligand(s) were synthesized and characterized. X-ray crystal structures of the bis-NHC complexes [IrIII(ttp)(IMe)2]+ (2a), [IrIII(oep)(BIMe)2]+ (2d), [IrIII(oep)(I i Pr)2]+ (2e) and [IrIII(F20tpp)(IMe)2]+ (2f) display ruffled porphyrin rings with mesocarbon displacements of 0.483-0.594 Å and long Ir-CNHC bonds of 2.100-2.152 Å. Variable-temperature 1H NMR analysis of 2a reveals that the macrocycle porphyrin ring inversion takes place in solution with an activation barrier of 40 ± 1 kJ mol-1. The UV-vis absorption spectra of IrIII(por)-NHC complexes display split Soret bands. TD-DFT calculations and resonance Raman experiments show that the higher-energy Soret band is derived from the 1MLCT dπ(Ir) → π*(por) transition. The near-infrared phosphorescence of IrIII(por)-NHC complexes from the porphyrin-based 3(π, π*) state features broad emission bands at 701-754 nm with low emission quantum yields and short lifetimes (Φ em < 0.01; τ < 4 μs). [IrIII(por)(IMe)2]+ complexes (por = ttp and oep) are efficient photosensitizers for 1O2 generation (Φ so = 0.64 and 0.88) and are catalytically active in the light-induced aerobic oxidation of secondary amines and arylboronic acid. The bis-NHC complexes exhibit potent dark cytotoxicity towards a panel of cancer cells with IC50 values at submicromolar levels. The cytotoxicity of these complexes could be further enhanced upon light irradiation with IC50 values as low as nanomolar levels in association with the light-induced generation of reactive oxygen species (ROS). Bioimaging of [IrIII(oep)(IMe)2]+ (2c) treated cells indicates that this Ir complex mainly targets the endoplasmic reticulum. [IrIII(oep)(IMe)2]+ catalyzes the photoinduced generation of singlet oxygen and triggers protein oxidation, cell cycle arrest, apoptosis and the inhibition of angiogenesis. It also causes pronounced photoinduced inhibition of tumor growth in a mouse model of human cancer.
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Affiliation(s)
- Tsz-Lung Lam
- State Key Laboratory of Synthetic Chemistry , Institute of Molecular Functional Materials , HKU-CAS Joint Laboratory on New Materials and Department of Chemistry , The University of Hong Kong , Pokfulam Road , Hong Kong , China .
| | - Ka-Chung Tong
- State Key Laboratory of Synthetic Chemistry , Institute of Molecular Functional Materials , HKU-CAS Joint Laboratory on New Materials and Department of Chemistry , The University of Hong Kong , Pokfulam Road , Hong Kong , China .
| | - Chen Yang
- State Key Laboratory of Synthetic Chemistry , Institute of Molecular Functional Materials , HKU-CAS Joint Laboratory on New Materials and Department of Chemistry , The University of Hong Kong , Pokfulam Road , Hong Kong , China . .,HKU Shenzhen Institute of Research and Innovation , Shenzhen , China
| | - Wai-Lun Kwong
- State Key Laboratory of Synthetic Chemistry , Institute of Molecular Functional Materials , HKU-CAS Joint Laboratory on New Materials and Department of Chemistry , The University of Hong Kong , Pokfulam Road , Hong Kong , China .
| | - Xiangguo Guan
- State Key Laboratory of Synthetic Chemistry , Institute of Molecular Functional Materials , HKU-CAS Joint Laboratory on New Materials and Department of Chemistry , The University of Hong Kong , Pokfulam Road , Hong Kong , China . .,HKU Shenzhen Institute of Research and Innovation , Shenzhen , China
| | - Ming-De Li
- State Key Laboratory of Synthetic Chemistry , Institute of Molecular Functional Materials , HKU-CAS Joint Laboratory on New Materials and Department of Chemistry , The University of Hong Kong , Pokfulam Road , Hong Kong , China .
| | - Vanessa Kar-Yan Lo
- State Key Laboratory of Synthetic Chemistry , Institute of Molecular Functional Materials , HKU-CAS Joint Laboratory on New Materials and Department of Chemistry , The University of Hong Kong , Pokfulam Road , Hong Kong , China .
| | - Sharon Lai-Fung Chan
- Department of Applied Biology and Chemical Technology , The Hong Kong Polytechnic University , Hung Hom , Hong Kong , China
| | - David Lee Phillips
- State Key Laboratory of Synthetic Chemistry , Institute of Molecular Functional Materials , HKU-CAS Joint Laboratory on New Materials and Department of Chemistry , The University of Hong Kong , Pokfulam Road , Hong Kong , China .
| | - Chun-Nam Lok
- State Key Laboratory of Synthetic Chemistry , Institute of Molecular Functional Materials , HKU-CAS Joint Laboratory on New Materials and Department of Chemistry , The University of Hong Kong , Pokfulam Road , Hong Kong , China .
| | - Chi-Ming Che
- State Key Laboratory of Synthetic Chemistry , Institute of Molecular Functional Materials , HKU-CAS Joint Laboratory on New Materials and Department of Chemistry , The University of Hong Kong , Pokfulam Road , Hong Kong , China . .,HKU Shenzhen Institute of Research and Innovation , Shenzhen , China
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