Ruthenium polypyridyl complexes have gained significant interest as photochemotherapies (PCTs) where their excited-state properties play a critical role in the photo-cytotoxicity mechanism and efficacy. Herein we report a systematic electrochemical, spectrochemical, and photophysical analysis of a series of ruthenium( ii ) polypyridyl complexes of the type [Ru(bpy) 2 (N–N)] 2+ (where bpy = 2,2′-bipyridine; N–N is a bidentate polypyridyl ligand) designed to mimic PCTs. In this series, the N–N ligand was modified through increased conjugation and/or incorporation of electronegative heteroatoms to shift the metal-to-ligand charge-transfer (MLCT) absorptions near the therapeutic window for PCTs (600–1100 nm) while incorporating steric bulk to trigger photoinduced ligand dissociation. The lowest energy MLCT absorptions were red-shifted from λ max = 454 nm to 564 nm, with emission energies decreasing from λ max = 620 nm to 850 nm. Photoinduced ligand ejection and temperature-dependent emission studies revealed an important interplay between red-shifting MLCT absorptions and accessing the dissociative 3 dd* states, with energy barriers between the 3 MLCT* and 3 dd* states ranging from 850 cm −1 to 2580 cm −1 for the complexes measured. This work demonstrates the importance of understanding both the MLCT manifold and 3 dd* state energy levels in the future design of ligands and complexes for PCT.
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Light‐responsive and Protic Ruthenium Compounds Bearing Bathophenanthroline and Dihydroxybipyridine Ligands Achieve Nanomolar Toxicity towards Breast Cancer Cells †
We report new ruthenium complexes bearing the lipophilic bathophenanthroline (BPhen) ligand and dihydroxybipyridine (dhbp) ligands which differ in the placement of the OH groups ([(BPhen)2Ru(n,n′‐dhbp)]Cl2with
- NSF-PAR ID:
- 10448412
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Photochemistry and Photobiology
- Volume:
- 98
- Issue:
- 1
- ISSN:
- 0031-8655
- Page Range / eLocation ID:
- p. 102-116
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract A new series of mono‐ and bis‐alkynyl CoIII(TIM) complexes (TIM=2,3,9,10‐tetramethyl‐1,4,8,11‐tetraazacyclotetradeca‐1,3,8,10‐tetraene) is reported herein. The
trans ‐[Co(TIM)(C2R)Cl]+complexes were prepared from the reaction betweentrans ‐[Co(TIM)Cl2]PF6and HC2R (R=tri(isopropyl)silyl or TIPS (1 ), ‐C6H4‐4‐tBu (2 ), ‐C6H4‐4‐NO2(3 a ), andN ‐mesityl‐1,8‐naphthalimide or NAPMes(4 a )) in the presence of Et3N. The intermediate complexes of the typetrans ‐[Co(TIM)(C2R)(NCMe)](PF6)(OTf),3 b and4 b , were obtained by treating3 a and4 a , respectively, with AgOTf in CH3CN. Furthermore, bis‐alkynyltrans ‐[Co(TIM)(C2R)2]PF6complexes,3 c and4 c , were generated following a second dehydrohalogenation reaction between3 b and4 b , respectively, and the appropriate HC2R in the presence of Et3N. These new complexes have been characterized using X‐ray diffraction (2 ,3 a ,4 a , and4 c ), IR,1H NMR, UV/Vis spectroscopy, fluorescent spectroscopy (4 c ), and cyclic voltammetry. -
null (Ed.)Exploiting earth-abundant iron-based metal complexes as high-performance photosensitizers demands long-lived electronically excited metal-to-ligand charge-transfer (MLCT) states, but these species suffer typically from femtosecond timescale charge-transfer (CT)-state quenching by low-lying nonreactive metal-centered (MC) states. Here, we engineer supermolecular Fe(II) chromophores based on the bis(tridentate-ligand)metal(II)-ethyne-(porphinato)zinc(II) conjugated framework, previously shown to give rise to highly delocalized low-lying 3 MLCT states for other Group VIII metal (Ru, Os) complexes. Electronic spectral, potentiometric, and ultrafast pump–probe transient dynamical data demonstrate that a combination of a strong σ-donating tridentate ligand and a (porphinato)zinc(II) moiety with low-lying π*-energy levels, sufficiently destabilize MC states and stabilize supermolecular MLCT states to realize Fe(II) complexes that express 3 MLCT state photophysics reminiscent of their heavy-metal analogs. The resulting Fe(II) chromophore archetype, FeNHCPZn, features a highly polarized CT state having a profoundly extended 3 MLCT lifetime (160 ps), 3 MLCT phosphorescence, and ambient environment stability. Density functional and domain-based local pair natural orbital coupled cluster [DLPNO-CCSD(T)] theory reveal triplet-state wavefunction spatial distributions consistent with electronic spectroscopic and excited-state dynamical data, further underscoring the dramatic Fe metal-to-extended ligand CT character of electronically excited FeNHCPZn. This design further prompts intense panchromatic absorptivity via redistributing high-energy absorptive oscillator strength throughout the visible spectral domain, while maintaining a substantial excited-state oxidation potential for wide-ranging photochemistry––highlighted by the ability of FeNHCPZn to photoinject charges into a SnO 2 /FTO electrode in a dye-sensitized solar cell (DSSC) architecture. Concepts enumerated herein afford opportunities for replacing traditional rare-metal–based emitters for solar-energy conversion and photoluminescence applications.more » « less
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Abstract Ru(II) complexes were synthesized with π‐expanding (phenyl, fluorenyl, phenanthrenyl, naphthalen‐1‐yl, naphthalene‐2‐yl, anthryl and pyrenyl groups) attached at a 1
H ‐imidazo[4,5‐f ][1,10]phenanthroline ligand and 4,4′‐dimethyl‐2,2′‐bipyridine (4,4′‐dmb) coligands. These Ru(II) complexes were characterized by 1D and 2D NMR, and mass spectroscopy, and studied for visible light and dark toxicity to human malignant melanoma SK‐MEL‐28 cells. In the SK‐MEL‐28 cells, the Ru(II) complexes are highly phototoxic (EC50 = 0.2–0.5 µm ) and have low dark toxicity (EC50 = 58–230 µm ). The highest phototherapeutic index (PI) of the series was found with the Ru(II) complex bearing the 2‐(pyren‐1‐yl)‐1H ‐imidazo[4,5‐f ][1,10]phenanthroline ligand. This high PI is in part attributed to the π‐rich character added by the pyrenyl group, and a possible low‐lying and longer‐lived3IL state due to equilibration with the3MLCT state. While this pyrenyl Ru(II) complex possessed a relatively high quantum yield for singlet oxygen formation (Φ∆ = 0.84), contributions from type‐I processes (oxygen radicals and radical ions) are competitive with the type‐II (1O2) process based on effects of added sodium azide and solvent deuteration. -
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We report on spectroscopic measurements on the 4
f 76s 28 S 7/2∘−4f 7(8 S ∘)6s 6p (1 P ∘)8 P 5/2,7/2transitions at 466.32 nm and 462.85 nm, respectively, in neutral europium-151 and europium-153. The center of gravity frequencies for the 151 and 153 isotopes for both transitions are reported for the first time using saturated absorption spectroscopy. For the 6s 6p (1 P ∘)8 P 5/2state, the center of gravity frequencies were found to be 642,894,493.3(4) MHz and 642,891,693.3(9) MHz for the 151 and 153 isotopes, respectively. The hyperfine constants for the upper state were found to beA (151)=−157.01(3)MHz,B (151)=74.5(4)MHz andA (153)=−69.43(14)MHz,B (153)=191.0(26)MHz. These hyperfine values are all consistent with previously published results except forB (151) that has a small discrepancy. The isotope shift was found to be 2799.54(20) MHz, a small discrepancy with previously published results. For the 6s 6p (1 P ∘)8P 7/2state, the center of gravity frequencies were found to be 647,708,930.6(6) MHz and 647,705,958.4(26) MHz for the 151 and 153 isotopes, respectively. The hyperfine constants for the upper state were found to beA (151)=−218.66(4)MHz,B (151)=−293.4(8)MHz andA (153)=−97.15(13)MHz,B (153)=−750(3)MHz. These values are all consistent with previously published results except forA (151) that has a small discrepancy. The isotope shift was found to be 2972.8(5) MHz, a small discrepancy with previously measured results.
