Long‐Lived Room‐Temperature Near‐IR Phosphorescence of BODIPY in a Visible‐Light‐Harvesting N^C^N PtII–Acetylide Complex with a Directly Metalated BODIPY Chromophore

Room‐temperature long‐lived near‐IR phosphorescence of boron‐dipyrromethene (BODIPY) was observed (λ_em=770 nm, Φ_P=3.5 %, τ_P=128.4 μs). Our molecular‐design strategy is to attach Pt^II coordination centers directly onto the BODIPY π‐core using acetylide bonds, rather than on the periphery of the BODIPY core, thus maximizing the heavy‐atom effect of Pt^II. In this case, the intersystem crossing (ISC) is facilitated and the radiative decay of the T₁ excited state of BODIPY is observed, that is, the phosphorescence of BODIPY. The complex shows strong absorption in the visible range (ε=53800 M ^?1 cm^?1 at 574 nm), which is rare for Pt^II–acetylide complexes. The complex is dual emissive with ³M LCT emission at 660 nm and the ³IL emission at 770 nm. The T₁ excited state of the complex is mainly localized on the BODIPY moiety (i.e. ³IL state, as determined by steady‐state and time‐resolved spectroscopy, 77 K emission spectra, and spin‐density analysis). The strong visible‐light‐harvesting ability and long‐lived T₁ excite state of the complex were used for triplet‐triplet annihilation based upconversion and an upconversion quantum yield of 5.2 % was observed. The overall upconversion capability (η=ε×Φ_UC) of this complex is remarkable considering its strong absorption. The model complex, without the BODIPY moiety, gives no upconversion under the same experimental conditions. Our work paves the way for access to transition‐metal complexes that show strong absorption of visible light and long‐lived ³IL excited states, which are important for applications in photovoltaics, photocatalysis, and upconversions, etc.     

Vectorial Electron Transfer in Donor–Photosensitizer–Acceptor Triads Based on Novel Bis‐tridentate Ruthenium Polypyridyl Complexes

The first examples of rodlike donor–photosensitizer–acceptor arrays based on bis‐2,6‐di(quinolin‐8‐yl)pyridine Ru^II complexes 1 a and 3 a for photoinduced electron transfer have been synthesized and investigated. The complexes are synthesized in a convergent manner and are isolated as linear, single isomers. Time‐resolved absorption spectroscopy reveals long‐lived, photoinduced charge‐separated states (τ_CSS ( 1 a )=140 ns, τ_CSS ( 3 a )=200 ns) formed by stepwise electron transfer. The overall yields of charge separation (≥50 % for complex 1 a and ≥95 % for complex 3 a ) are unprecedented for bis‐tridentate Ru^II polypyridyl complexes. This is attributed to the long‐lived excited state of the [Ru(dqp)₂]²⁺ complex combined with fast electron transfer from the donor moiety following the initial charge separation. The rodlike arrangement of donor and acceptor gives controlled, vectorial electron transfer, free from the complications of stereoisomeric diversity. Thus, such arrays provide an excellent system for the study of photoinduced electron transfer and, ultimately, the harvesting of solar energy.     

Synergistic Effects of Metals in a Promising RuII−PtII Assembly for a Combined Anticancer Approach: Theoretical Exploration of the Photophysical Properties

Ru^II?Pt^II complexes are a class of bioactive molecules of interest as anticancer agents that combine a light‐absorbing chromophore with a cisplatin‐like unit. The results of a DFT and TDDFT investigation of a Ru^II complex and its conjugate with a cis‐PtCl₂ moiety reveal that a synergistic effect of the metals makes the assembly a promising multitarget anticancer drug. Inspection of type I and type II photoreactions and spin–orbit coupling computations reveals that the cis‐PtCl₂ moiety improves the photophysical properties of the Ru^II chromophore, ensuring efficient singlet oxygen generation and making the assembly suitable for photodynamic therapy. At the same time, the Ru^II chromophore promotes a new alternative activation mechanism of the Pt^II ligand via a triplet metal‐to‐ligand charge transfer (³M LCT) state, before reaching the biological target. The importance of the supramolecular architecture is accurately derived, opening interesting new perspectives on the use of bimetallic Ru^II?Pt^II assemblies in a combined anticancer approach.     

Pd–Porphyrin Oligomers Sensitized for Green‐to‐Blue Photon Upconversion: The More the Better?

A series of directly meso‐meso‐linked Pd–porphyrin oligomers (PdDTP‐M, PdDTP‐D, and PdDTP‐T) have been prepared. The absorption region and the light‐harvesting ability of the Pd–porphyrin oligomers are broadened and enhanced by increasing the number of Pd–porphyrin units. Triplet–triplet annihilation upconversion (TTA‐UC) systems were constructed by utilizing the Pd–porphyrin oligomers as the sensitizer and 9,10‐diphenylanthracene (DPA) as the acceptor in deaerated toluene and green‐to‐blue photon upconversion was observed upon excitation with a 532 nm laser. The triplet–triplet annihilation upconversion quantum efficiencies were found to be 6.2 %, 10.5 %, and 1.6 % for the [PdDTP‐M]/DPA, [PdDTP‐D]/DPA, and [PdDTP‐T]/DPA systems, respectively, under an excitation power density of 500 mW cm^?2. The photophysical processes of the TTA‐UC systems have been investigated in detail. The higher triplet–triplet annihilation upconversion quantum efficiency observed in the [PdDTP‐D]/DPA system can be rationalized by the enhanced light‐harvesting ability of PdDTP‐D at 532 nm. Under the same experimental conditions, the [PdDTP‐D]/DPA system produces more ³DPA* than the other two TTA‐UC systems, benefiting the triplet–triplet annihilation process. This work provides a useful way to develop efficient TTA‐UC systems with broad spectral response by using Pd–porphyrin oligomers as sensitizers.     

Ruthenium(II)-polyimine-coumarin light-harvesting molecular arrays: design rationale and application for triplet-triplet-annihilation-based upconversion

Ru(II)-bis-pyridine complexes typically absorb below 450?nm in the UV spectrum and their molar extinction coefficients are only moderate (ε<16,000 M(-1) cm(-1)). Thus, Ru(II)-polyimine complexes that show intense visible-light absorptions are of great interest. However, no effective light-harvesting ruthenium(II)/organic chromophore arrays have been reported. Herein, we report the first visible-light-harvesting Ru(II)-coumarin arrays, which absorb at 475?nm (ε up to 63,300 M(-1) cm(-1), 4-fold higher than typical Ru(II)-polyimine complexes). The donor excited state in these arrays is efficiently converted into an acceptor excited state (i.e., efficient energy-transfer) without losses in the phosphorescence quantum yield of the acceptor. Based on steady-state and time-resolved spectroscopy and DFT calculations, we proposed a general rule for the design of Ru(II)-polypyridine-chromophore light-harvesting arrays, which states that the (1)IL energy level of the ligand must be close to the respective energy level of the metal-to-ligand charge-transfer (MLCT) states. Lower energy levels of (1)IL/(3)IL than the corresponding (1)MLCT/(3)MLCT states frustrate the cascade energy-transfer process and, as a result, the harvested light energy cannot be efficiently transferred to the acceptor. We have also demonstrated that the light-harvesting effect can be used to improve the upconversion quantum yield to 15.2?% (with 9,10-diphenylanthracene as a triplet-acceptor/annihilator), compared to the parent complex without the coumarin subunit, which showed an upconversion quantum yield of only 0.95?%.     

Synthesis,Electrochemistry, and Photophysical Studies of Ruthenium(II) Polypyridine Complexes with D–π–A–π–D Type Ligands and Their Application Studies as Organic Memories

A new class of ruthenium(II) polypyridine complexes with a series of D–π–A–π–D type (D=donor, A=acceptor) ligands was synthesized and characterized by ¹H NMR spectroscopy, mass spectrometry, and elemental analysis. The photophysical and electrochemical properties of the complexes were also investigated. The newly synthesized ruthenium(II) polypyridine complexes were found to exhibit two intense absorption bands at both high‐energy (λ=333–369 nm) and low‐energy (λ=520–535 nm) regions. They are assigned as intraligand (IL) π→π* transitions of the bipyridine (bpy) and π‐conjugated bpy ligands, and IL charge‐transfer (CT) transitions from the donor to the acceptor moiety with mixing of dπ(Ru^II)→π*(bpy) and dπ(Ru^II)→π*(L) MLCT characters, respectively. In addition, all complexes were demonstrated to exhibit intense red emissions at approximately λ=727–744 nm in degassed dichloromethane at 298 K or in n‐butyronitrile glass at 77 K. Nanosecond transient absorption (TA) spectroscopy has also been carried out, establishing the presence of the charge‐separated state. In order to understand the electrochemical properties of the complexes, cyclic voltammetry has also been performed. Two quasi‐reversible oxidation couples and three quasi‐reversible reduction couples were observed. One of the ruthenium(II) complexes has been utilized in the fabrication of memory devices, in which an ON/OFF current ratio of over 10⁴ was obtained.     

Long‐Lived Room‐Temperature Deep‐Red‐Emissive Intraligand Triplet Excited State of Naphthalimide in Cyclometalated IrIII Complexes and its Application in Triplet‐Triplet Annihilation‐Based Upconversion

Cyclometalated Ir^III complexes with acetylide ppy and bpy ligands were prepared (ppy=2‐phenylpyridine, bpy=2,2′‐bipyridine) in which naphthal ( Ir‐2 ) and naphthalimide (NI) were attached onto the ppy ( Ir‐3 ) and bpy ligands ( Ir‐4 ) through acetylide bonds. [Ir(ppy)₃] ( Ir‐1 ) was also prepared as a model complex. Room‐temperature phosphorescence was observed for the complexes; both neutral and cationic complexes Ir‐3 and Ir‐4 showed strong absorption in the visible range (ε=39600 M ^?1 cm^?1 at 402 nm and ε=25100 M ^?1 cm^?1 at 404 nm, respectively), long‐lived triplet excited states (τ_T=9.30 μs and 16.45 μs) and room‐temperature red emission (λ_em=640 nm, Φ_p=1.4 % and λ_em=627 nm, Φ_p=0.3 %; cf. Ir‐1 : ε=16600 M ^?1 cm^?1 at 382 nm, τ_em=1.16 μs, Φ_p=72.6 %). Ir‐3 was strongly phosphorescent in non‐polar solvent (i.e., toluene), but the emission was completely quenched in polar solvents (MeCN). Ir‐4 gave an opposite response to the solvent polarity, that is, stronger phosphorescence in polar solvents than in non‐polar solvents. Emission of Ir‐1 and Ir‐2 was not solvent‐polarity‐dependent. The T₁ excited states of Ir‐2 , Ir‐3 , and Ir‐4 were identified as mainly intraligand triplet excited states (³IL) by their small thermally induced Stokes shifts (ΔE_s), nanosecond time‐resolved transient difference absorption spectroscopy, and spin‐density analysis. The complexes were used as triplet photosensitizers for triplet‐triplet annihilation (TTA) upconversion and quantum yields of 7.1 % and 14.4 % were observed for Ir‐2 and Ir‐3 , respectively, whereas the upconversion was negligible for Ir‐1 and Ir‐4 . These results will be useful for designing visible‐light‐harvesting transition‐metal complexes and for their applications as triplet photosensitizers for photocatalysis, photovoltaics, TTA upconversion, etc.     

Light Harvesting and Directional Energy Transfer in Long‐Lived Homo‐ and Heterotrimetallic Complexes of FeII,RuII, and OsII

A new family of trimetallic complexes of the form [(bpy)₂M(phen‐Hbzim‐tpy)M′(tpy‐Hbzim‐phen)M(bpy)₂]⁶⁺ (M=Ru^II, Os; M′=Fe^II, Ru^II, Os; bpy=2,2′‐bipyridine) derived from heteroditopic phenanthroline–terpyridine bridge 2‐{4‐[2,6‐di(pyridin‐2‐yl) pyridine‐4‐yl]phenyl}‐1H‐imidazole[4,5‐f][1,10]phenanthroline (phen‐Hbzim‐tpy) were prepared and fully characterized. Zn²⁺ was used to prepare mixed‐metal trimetallic complexes in situ by coordinating with the free tpy site of the monometallic precursors. The complexes show intense absorptions throughout the UV/Vis region and also exhibit luminescence at room temperature. The redox behavior of the compounds is characterized by several metal‐centered reversible oxidation and ligand‐centered reduction processes. Steady‐state and time‐resolved luminescence data show that the potentially luminescent Ru^II‐ and Os^II‐based triplet metal‐to‐ligand charge‐transfer (³MLCT) excited states in the triads are quantitatively quenched, most likely by intercomponent energy transfer to the lower lying ³MLCT (for Ru and Os) or triplet metal‐centered (³MC) excited states of the Fe^II subunit (nonluminescent). Interestingly, iron did not adversely affect the photophysics of the respective systems. This suggests that the multicomponent molecular‐wire‐like complexes investigated here can behave as efficient light‐harvesting antennas, because all the light absorbed by the various subunits is efficiently channeled to the subunit(s) in which the lowest‐energy excited states are located.     

Broadband Visible‐Light‐Harvesting trans‐Bis(alkylphosphine) Platinum(II)‐Alkynyl Complexes with Singlet Energy Transfer between BODIPY and Naphthalene Diimide Ligands

A heteroleptic bis(tributylphosphine) platinum(II)‐alkynyl complex ( Pt‐1 ) showing broadband visible‐light absorption was prepared. Two different visible‐light‐absorbing ligands, that is, ethynylated boron‐dipyrromethene (BODIPY) and a functionalized naphthalene diimide (NDI) were used in the molecule. Two reference complexes, Pt‐2 and Pt‐3 , which contain only the NDI or BODIPY ligand, respectively, were also prepared. The coordinated BODIPY ligand shows absorption at 503 nm and fluorescence at 516 nm, whereas the coordinated NDI ligand absorbs at 594 nm; the spectral overlap between the two ligands ensures intramolecular resonance energy transfer in Pt‐1 , with BODIPY as the singlet energy donor and NDI as the energy acceptor. The complex shows strong absorption in the region 450 nm–640 nm, with molar absorption coefficient up to 88 000 M ^?1 cm^?1. Long‐lived triplet excited states lifetimes were observed for Pt‐1 – Pt‐3 (36.9 μs, 28.3 μs, and 818.6 μs, respectively). Singlet and triplet energy transfer processes were studied by the fluorescence/phosphorescence excitation spectra, steady‐state and time‐resolved UV/Vis absorption and luminescence spectra, as well as nanosecond time‐resolved transient difference absorption spectra. A triplet‐state equilibrium was observed for Pt‐1 . The complexes were used as triplet photosensitizers for triplet–triplet annihilation upconversion, with upconversion quantum yields up to 18.4 % being observed for Pt‐1 .     

A Ruthenium Complex–Porphyrin–Fullerene‐Linked Molecular Pentad as an Integrative Photosynthetic Model

A ruthenium complex, porphyrin sensitizer, fullerene acceptor molecular pentad has been synthesized and a long‐lived hole–electron pair was achieved in aqueous solution by photoinduced multistep electron transfer: Upon irradiation by visible light, the excited‐state of a zinc porphyrin (¹ZnP*) was quenched by fullerene (C₆₀) to afford a radical ion pair, ^1,3(ZnP^.+‐C₆₀^.−). This was followed by the subsequent electron transfer from a water oxidation catalyst unit (Ru^II) to ZnP^.+ to give the long‐lived charge‐separated state, Ru^III‐ZnP‐C₆₀^.−, with a lifetime of 14 μs. The ZnP worked as a visible‐light‐harvesting antenna, while the C₆₀ acted as an excellent electron acceptor. As a consequence, visible‐light‐driven water oxidation by this integrated photosynthetic model compound was achieved in the presence of sacrificial oxidant and redox mediator.     

New Anthracene Derivatives as Triplet Acceptors for Efficient Green‐to‐Blue Low‐Power Upconversion

Three new anthracene derivatives [2‐chloro‐9,10‐dip‐tolylanthracene (DTACl), 9,10‐dip‐tolylanthracene‐2‐carbonitrile (DTACN), and 9,10‐di(naphthalen‐1‐yl)anthracene‐2‐carbonitrile (DNACN)] were synthesized as triplet acceptors for low‐power upconversion. Their linear absorption, single‐photon‐excited fluorescence, and upconversion fluorescence properties were studied. The acceptors exhibit high fluorescence yields in DMF. Selective excitation of the sensitizer Pd^IIoctaethylporphyrin (PdOEP) in solution containing DTACl, DTACN, or DNA‐CN at 532 nm with an ultralow excitation power density of 0.5 W cm^?2 results in anti‐Stokes blue emission. The maximum upconversion quantum yield (Φ_UC=17.4 %) was obtained for the couple PdOEP/DTACl. In addition, the efficiency of the triplet–triplet energy transfer process was quantitatively studied by quenching experiments. Experimental results revealed that a highly effective acceptor for upconversion should combine high fluorescence quantum yields with efficient quenching of the sensitizer triplet.     

Iridium(III) Complexes Bearing Pyrene‐Functionalized 1,10‐Phenanthroline Ligands as Highly Efficient Sensitizers for Triplet–Triplet Annihilation Upconversion

“Chemistry‐on‐the‐complex” synthetic methods have allowed the selective addition of 1‐ethynylpyrene appendages to the 3‐, 5‐, 3,8‐ and 5,6‐positions of Ir^III‐coordinated 1,10‐phenanthroline via Sonogashira cross‐coupling. The resulting suite of complexes has given rise to the first rationalization of their absorption and emission properties as a function of the number and position of the pyrene moieties. Strong absorption in the visible region (e.g. 3,8‐substituted Ir‐3 : λ_abs=481 nm, ?=52 400 m ^?1 cm^?1) and long‐lived triplet excited states (e.g. 5‐substituted Ir‐2 : τ_T=367.7 μs) were observed for the complexes in deaerated CH₂Cl₂. On testing the series as triplet sensitizers for triplet–triplet annihilation upconversion, those Ir^III complexes bearing pyrenyl appendages at the 3‐ and 3,8‐positions ( Ir‐1 , Ir‐3 ) were found to give optimal upconversion quantum yields (30.2 % and 31.6 % respectively).     

Broadband Light‐Harvesting Molecular Triads with High FRET Efficiency Based on the Coumarin–Rhodamine–BODIPY Platform

Broadband capturing and FRET‐based light‐harvesting molecular triads, CRBs, based on the coumarin–rhodamine–BODIPY platform were rationally designed and synthesized. The absorption band of CRBs starts from blue–green to yellow–orange regions (330–610 nm), covering the strong radiation scope of sunlight. The peripheral coumarin and BODIPY chromophore energy could transfer to the central acceptor rhodamine by a one‐step direct way. The energy of the coumarin moiety could also transfer to the BODIPY unit, subsequently transferring to the rhodamine core by two‐step sequential ways. Both the efficiencies of the coumarin moiety and the BODIPY unit to the rhodamine core in CRBs, determined by two different ways, are very high.     

Light‐Harvesting Photocatalysis for Water Oxidation Using Mesoporous Organosilica

An organic‐based photocatalysis system for water oxidation, with visible‐light harvesting antennae, was constructed using periodic mesoporous organosilica (PMO). PMO containing acridone groups in the framework (Acd‐PMO), a visible‐light harvesting antenna, was supported with [Ru^II(bpy)₃²⁺] complex (bpy=2,2′‐bipyridyl) coupled with iridium oxide (IrO_x) particles in the mesochannels as photosensitizer and catalyst, respectively. Acd‐PMO absorbed visible light and funneled the light energy into the Ru complex in the mesochannels through excitation energy transfer. The excited state of Ru complex is oxidatively quenched by a sacrificial oxidant (Na₂S₂O₈) to form Ru³⁺ species. The Ru³⁺ species extracts an electron from IrO_x to oxidize water for oxygen production. The reaction quantum yield was 0.34 %, which was improved to 0.68 or 1.2 % by the modifications of PMO. A unique sequence of reactions mimicking natural photosystem II, 1) light‐harvesting, 2) charge separation, and 3) oxygen generation, were realized for the first time by using the light‐harvesting PMO.     

Ultrafast Photoinduced Charge Separation in Wide‐Band‐Capturing Self‐Assembled Supramolecular Bis(donor styryl)BODIPY–Fullerene Conjugates

A new series of self‐assembled supramolecular donor–acceptor conjugates capable of wide‐band capture, and exhibiting photoinduced charge separation have been designed, synthesized and characterized using various techniques as artificial photosynthetic mimics. The donor host systems comprise of a 4,4‐difluoro‐4‐bora‐3a,4a‐diaza‐s‐indacene (BODIPY) containing a crown ether entity at the meso‐position and two styryl entities on the pyrrole rings. The styryl end groups also carried additional donor (triphenylamine or phenothiazine) entities. The acceptor host system was a fulleropyrrolidine comprised of an ethylammonium cation. Owing to the presence of extended conjugation and multiple chromophore entities, the BODIPY host revealed absorbance and emission well into the near‐IR region covering the 300–850 nm spectral range. The donor–acceptor conjugates formed by crown ether–alkyl ammonium cation binding of the host–guest system was characterized by optical absorbance and emission, computational, and electrochemical techniques. Experimentally determined binding constants were in the range of 1–2×10⁵ M ^?1. An energy‐level diagram to visualize different photochemical events was established using redox, computational, absorbance, and emission data. Spectral evidence for the occurrence of photoinduced charge separation in these conjugates was established from femtosecond transient absorption studies. The measured rates indicated ultrafast charge separation and relatively slow charge recombination revealing their usefulness in light‐energy harvesting and optoelectronic device applications. The bis(donor styryl)BODIPY‐derived conjugates populated their triplet excited states during charge recombination.     

Bright Fluorescence and Host–Guest Sensing with a Nanoscale M4L6 Tetrahedron Accessed by Self‐Assembly of Zinc–Imine Chelate Vertices and Perylene Bisimide Edges

A highly luminescent Zn₄L₆ tetrahedron is reported with 3.8 nm perylene bisimide edges and hexadentate Zn^II–imine chelate vertices. Replacing Fe^II and monoamines commonly utilized in subcomponent self‐assembly with Zn^II and tris(2‐aminoethyl)amine provides access to a metallosupramolecular host with the rare combination of structural integrity at concentrations <10^?7 mol L^?1 and an exceptionally high fluorescence quantum yield of Φ_em=0.67. Encapsulation of multiple perylene or coronene guest molecules is accompanied by strong luminescence quenching. We anticipate this self‐assembly strategy may be generalized to improve access to brightly fluorescent coordination cages tailored for host–guest light‐harvesting, photocatalysis, and sensing.     

Cyclometalated Ruthenium(II) Complexes Featuring Tridentate Click‐Derived Ligands for Dye‐Sensitized Solar Cell Applications

A series of heteroleptic bis(tridentate) Ru^II complexes featuring N^C^N‐cyclometalating ligands is presented. The 1,2,3‐triazole‐containing tridentate ligands are readily functionalized with hydrophobic side chains by means of click chemistry and the corresponding cyclometalated Ru^II complexes are easily synthesized. The performance of these thiocyanate‐free complexes in a dye‐sensitized solar cell was tested and a power conversion efficiency (PCE) of up to 4.0 % (J_sc=8.1 mA cm^?2, V_oc=0.66 V, FF=0.70) was achieved, while the black dye ((NBu₄)₃[Ru(Htctpy)(NCS)₃]; Htctpy=2,2′:6′,2′′‐terpyridine‐4′‐carboxylic acid‐4,4′′‐dicarboxylate) showed 5.2 % (J_sc=10.7 mA cm^?2, V_oc=0.69 V, FF=0.69) under comparable conditions. When co‐adsorbed with chenodeoxycholic acid, the PCE of the best cyclometalated dye could be improved to 4.5 % (J_sc=9.4 mA cm^?2, V_oc=0.65 V, FF=0.70). The PCEs correlate well with the light‐harvesting capabilities of the dyes, while a comparable incident photon‐to‐current efficiency was achieved with the cyclometalated dye and the black dye. Regeneration appeared to be efficient in the parent dye, despite the high energy of the highest occupied molecular orbital. The device performance was investigated in more detail by electrochemical impedance spectroscopy. Ultimately, a promising Ru^II sensitizer platform is presented that features a highly functionalizable “click”‐derived cyclometalating ligand.     

Donor–Acceptor Heterojunction Configurations Based on DNA–Multichromophore Arrays

Multichromophore arrays of bis(2‐thienyl)diketopyrrolopyrrole (DPP) and naphthalenediimide (NDI) with two Zn^II‐cyclens were constructed using thymidine DNA as a scaffold through the binding of the Zn^II‐cyclens with thymine bases. We demonstrate photocurrent generation in a donor–acceptor heterojunction configuration consisting of the DPP (donor) and NDI (acceptor) arrays co‐immobilized on an Au electrode. The co‐immobilized electrode exhibited good photocurrent responses because of the efficient charge separation between the DPP and NDI arrays. In contrast, an immobilized electrode consisting of randomly assembled DPP‐NDI arrays generated no photocurrent response because DPP formed ground‐state charge‐transfer complexes with NDI in the randomly assembled arrays. Therefore, our approach to generate donor–acceptor heterojunctions based on DNA–multichromophore arrays is a useful method to efficiently generate photocurrent.     

Spontaneous CO Release from RuII(CO)2–Protein Complexes in Aqueous Solution,Cells, and Mice

We demonstrate that Ru^II(CO)₂–protein complexes, formed by the reaction of the hydrolytic decomposition products of [fac‐RuCl(κ²‐H₂NCH₂CO₂)(CO)₃] (CORM‐3) with histidine residues exposed on the surface of proteins, spontaneously release CO in aqueous solution, cells, and mice. CO release was detected by mass spectrometry (MS) and confocal microscopy using a CO‐responsive turn‐on fluorescent probe. These findings support our hypothesis that plasma proteins act as CO carriers after in vivo administration of CORM‐3. CO released from a synthetic bovine serum albumin (BSA)–Ru^II(CO)₂ complex leads to downregulation of the cytokines interleukin (IL)‐6, IL‐10, and tumor necrosis factor (TNF)‐α in cancer cells. Finally, administration of BSA–Ru^II(CO)₂ in mice bearing a colon carcinoma tumor results in enhanced CO accumulation at the tumor. Our data suggest the use of Ru^II(CO)₂–protein complexes as viable alternatives for the safe and spatially controlled delivery of therapeutic CO in vivo.     

Spontaneous CO Release from RuII(CO)2–Protein Complexes in Aqueous Solution,Cells, and Mice

We demonstrate that Ru^II(CO)₂–protein complexes, formed by the reaction of the hydrolytic decomposition products of [fac‐RuCl(κ²‐H₂NCH₂CO₂)(CO)₃] (CORM‐3) with histidine residues exposed on the surface of proteins, spontaneously release CO in aqueous solution, cells, and mice. CO release was detected by mass spectrometry (MS) and confocal microscopy using a CO‐responsive turn‐on fluorescent probe. These findings support our hypothesis that plasma proteins act as CO carriers after in vivo administration of CORM‐3. CO released from a synthetic bovine serum albumin (BSA)–Ru^II(CO)₂ complex leads to downregulation of the cytokines interleukin (IL)‐6, IL‐10, and tumor necrosis factor (TNF)‐α in cancer cells. Finally, administration of BSA–Ru^II(CO)₂ in mice bearing a colon carcinoma tumor results in enhanced CO accumulation at the tumor. Our data suggest the use of Ru^II(CO)₂–protein complexes as viable alternatives for the safe and spatially controlled delivery of therapeutic CO in vivo.