3652-92-4Relevant academic research and scientific papers
Photocatalytic Reduction of CO2 with Re-Pyridyl-NHCs
Huckaba, Aron J.,Sharpe, Emily Anne,Delcamp, Jared H.
, p. 682 - 690 (2016)
A series of Re(I) pyridyl N-heterocyclic carbene (NHC) complexes have been synthesized and examined in the photocatalytic reduction of CO2 using a simulated solar spectrum. The catalysts were characterized through NMR, UV-vis, cyclic voltammetry under nitrogen, and cyclic voltammetry under carbon dioxide. The complexes were compared directly with a known benchmark catalyst, Re(bpy) (CO)3Br. An electron-deficient NHC substituent (PhCF3) was found to promote catalytic activity when compared with electron-neutral and -rich substituents. Re(PyNHC-PhCF3) (CO)3Br was found to exceed the CO production of the benchmark Re(bpy) (CO)3Br catalyst (51 vs 33 TON) in the presence of electron donor BIH and photosensitizer fac-Ir(ppy)3. Importantly, Re(PyNHC-PhCF3) (CO)3Br was found to function without a photosensitizer (32 TON) at substantially higher turnovers than the benchmark catalyst Re(bpy) (CO)3Br (14 TON) under a solar simulated spectrum.
Earth-abundant photocatalytic systems for the visible-light-driven reduction of CO2 to CO
Rosas-Hernández, Alonso,Steinlechner, Christoph,Junge, Henrik,Beller, Matthias
, p. 2356 - 2360 (2017)
Herein, we report a highly selective photocatalytic system, based on an in situ copper photosensitizer and an iron catalyst, for the reduction of CO2 to CO. Turnover numbers (TON) up to 487 (5 h) with selectivities up to 99% and ΦCO = 13.3% were observed. Stern-Volmer analysis allowed us to establish a reductive quenching mechanism between the Cu PS and electron donor.
Host–Guest Interactions in a Metal–Organic Framework Isoreticular Series for Molecular Photocatalytic CO2 Reduction
Casini, Angela,Fischer, Roland A.,Haimerl, Johanna,Rieger, Bernhard,Schuster, Michael,Shustova, Natalia B.,Stanley, Philip M.,Thomas, Christopher,Urstoeger, Alexander,Warnan, Julien
, p. 17854 - 17860 (2021)
A strategy to improve homogeneous molecular catalyst stability, efficiency, and selectivity is the immobilization on supporting surfaces or within host matrices. Herein, we examine the co-immobilization of a CO2 reduction catalyst [ReBr(CO)3(4,4′-dcbpy)] and a photosensitizer [Ru(bpy)2(5,5′-dcbpy)]Cl2 using the isoreticular series of metal–organic frameworks (MOFs) UiO-66, -67, and -68. Specific host pore size choice enables distinct catalyst and photosensitizer spatial location—either at the outer MOF particle surface or inside the MOF cavities—affecting catalyst stability, electronic communication between reaction center and photosensitizer, and consequently the apparent catalytic rates. These results allow for a rational understanding of an optimized supramolecular layout of catalyst, photosensitizer, and host matrix.
Reactivities of five-membered heterocycles in hydride transfer reactions in-sook
Lee, Han,Jeoung, Eun Hee
, p. 7275 - 7279 (1998)
2-[2′- And 3-furyl and thienyl]-1,1,3-dimethylbenzimidazoline derivatives have been prepared in order to measure the rate of oxidation of these compounds by l-benzyl-3-carbamoylpyridinium ion and by l-benzyl-5-nitroisoquinolinium ion. The reactions were monitored spectrophotometrically in a solvent consisting of four parts of 2-propanol and one part of water at 25 °C. The reactivities of the five-membered heterocycles fail to correlate with the acid dissociation constants, pKa, of the corresponding heteroaromatic carboxylic acids. The variations in k2 appear to depend more heavily on resonance involving the heteroatoms while the pKa seems to depend mainly on the inductive effect of the heteroatoms. When rate constants for oxidation by the l-benzyl-5-nitroisoquinolinium ion are plotted against rate constants for oxidation of the same imidazoline derivatives by l-benzyl3-carbamoylpyridinium ion, a linear plot with a slope of 0.96 ±0.06 is obtained. The slope of this plot can be estimated, using Marcus theory, by taking the rates of the two calculated a values. In this way 0.95 is obtained, in good agreement with the experimental value. In this calculation it was assumed that the reactivity of isoquinolinium is about the same as that of phenanthridinium ion. These results further extend the generality of the one-step mechanism of hydride transfer, without the intervention of high-energy intermediates.
Visible light-mediated metal-free double bond deuteration of substituted phenylalkenes
Iakovenko, Roman,Hlavá?, Jan
supporting information, p. 440 - 446 (2021/01/28)
Various bromophenylalkenes were reductively photodebrominated by using 1,3-dimethyl-2-phenyl-1H-benzo-[d]imidazoline (DMBI) and 9,10-dicyanoanthracene. With deuterated DMBI analogs (the most effective was DMBI-d11), satisfactory to excellent isotopic yields were obtained. DMBI-d11 could also be regenerated from the reaction mixtures with a recovery rate of up to 50%. The combination of the photodebromination reaction with conventional methods for bromoalkene synthesis enables sequential monodeuteration of a double bond without the necessity of a metal catalyst. This journal is
Unexpected Roles of Triethanolamine in the Photochemical Reduction of CO2 to Formate by Ruthenium Complexes
Sampaio, Renato N.,Grills, David C.,Polyansky, Dmitry E.,Szalda, David J.,Fujita, Etsuko
, p. 2413 - 2428 (2020/02/13)
A series of 4,4′-dimethyl-2,2′-bipyridyl ruthenium complexes with carbonyl ligands were prepared and studied using a combination of electrochemical and spectroscopic methods with infrared detection to provide structural information on reaction intermediates in the photochemical reduction of CO2 to formate in acetonitrile (CH3CN). An unsaturated 5-coordinate intermediate was characterized, and the hydride-transfer step to CO2 from a singly reduced metal-hydride complex was observed with kinetic resolution. While triethanolamine (TEOA) was expected to act as a proton acceptor to ensure the sacrificial behavior of 1,3-dimethyl-2-phenyl-2,3-dihydro-1H-benzo[d]imidazole as an electron donor, time-resolved infrared measurements revealed that about 90% of the photogenerated one-electron reduced complexes undergo unproductive back electron transfer. Furthermore, TEOA showed the ability to capture CO2 from CH3CN solutions to form a zwitterionic alkylcarbonate adduct and was actively engaged in key catalytic steps such as metal-hydride formation, hydride transfer to CO2 to form the bound formate intermediate, and dissociation of formate ion product. Collectively, the data provide an overview of the transient intermediates of Ru(II) carbonyl complexes and emphasize the importance of considering the participation of TEOA when investigating and proposing catalytic pathways.
Rediscovering aminal chemistry: Copper(ii) catalysed formation under mild conditions
Afonso, Carlos A. M.,António, Jo?o P. M.,Gomes, Rafael F. A.,Mendon?a, Ricardo,Pereira, Juliana G.
supporting information, p. 7484 - 7490 (2020/11/18)
Aminals, the N,N analogues of acetals, have been thoroughly explored in organic chemistry, with a particular focus on heteroaromatic aldehyde lithiation. Nevertheless, the existing methodologies for their formation typically employ harsh conditions limiting their usefulness. In this work, we present an efficient and mild methodology for the preparation of aminals from aromatic aldehydes, including furanic platforms. These mild conditions allowed ease of access to a plethora of aminals and as such we set out to explore previously unaccessible potential applications. By studying the stability of various aminals, we were able to develop a simple aldehyde protecting group based on a commercial diamine which is deprotected under mind conditions. We developed a protocol for the scavenging of genotoxic aldehydes by taking advantage of our methodology and a diamine resin, as well as early studies on the development of a stimuli-responsive release system using a salycil aldehyde derived aminal. This journal is
Molecular Porous Photosystems Tailored for Long-Term Photocatalytic CO2 Reduction
Alves-Favaro, Marcelo,Canivet, Jér?me,Duguet, Mathis,Farrusseng, David,Ghosh, Ashta C.,Lorentz, Chantal,Mellot-Draznieks, Caroline,Mohr, Yorck,Palkovits, Regina,Perrinet, Quentin,Quadrelli, Elsje Alessandra,Wisser, Florian M.,de Waele, Vincent
supporting information, p. 5116 - 5122 (2020/02/20)
The molecular-level structuration of two full photosystems into conjugated porous organic polymers is reported. The strategy of heterogenization gives rise to photosystems which are still fully active after 4 days of continuous illumination. Those materials catalyze the carbon dioxide photoreduction driven by visible light to produce up to three grams of formate per gram of catalyst. The covalent tethering of the two active sites into a single framework is shown to play a key role in the visible light activation of the catalyst. The unprecedented long-term efficiency arises from an optimal photoinduced electron transfer from the light harvesting moiety to the catalytic site as anticipated by quantum mechanical calculations and evidenced by in situ ultrafast time-resolved spectroscopy.
Tracking Mechanistic Pathway of Photocatalytic CO2 Reaction at Ni Sites Using Operando, Time-Resolved Spectroscopy
Hu, Yangguang,Zhan, Fei,Wang, Qian,Sun, Yujian,Yu, Can,Zhao, Xuan,Wang, Hao,Long, Ran,Zhang, Guozhen,Gao, Chao,Zhang, Wenkai,Jiang, Jun,Tao, Ye,Xiong, Yujie
supporting information, p. 5618 - 5626 (2020/04/09)
Harvesting solar energy for catalytic conversion of CO2 into valuable chemical fuels/feedstocks is an attractive yet challenging strategy to realize a sustainable carbon-cycle utilization. Homogeneous catalysts typically exhibit higher activity and selectivity as compared with heterogeneous counterparts, benefiting from their atomically dispersed catalytic sites and versatile coordination structures. However, it is still a black box how the coordination and electronic structures of catalysts dynamically evolve during the reaction, forming the bottleneck for understanding their reaction pathways. Herein, we demonstrate to track the mechanistic pathway of photocatalytic CO2 reduction using a terpyridine nickel(II) complex as a catalyst model. Integrated with a typical homogeneous photosensitizer, the catalytic system offers a high selectivity of 99% for CO2-to-CO conversion with turnover number and turnover frequency as high as 2.36 × 107 and 385.6 s-1, respectively. We employ operando and time-resolved X-ray absorption spectroscopy, in combination with other in situ spectroscopic techniques and theoretical computations, to track the intermediate species of Ni catalyst in the photocatalytic CO2 reduction reaction for the first time. Taken together with the charge dynamics resolved by optical transient absorption spectroscopy, the investigation elucidates the full mechanistic reaction pathway including some key factors that have been often overlooked. This work opens the black box for CO2 reduction in the system of homogeneous catalysts and provides key information for developing efficient catalysts toward artificial photosynthesis.
An unexpected iron (II)-based homogeneous catalytic system for highly efficient CO2-to-CO conversion under visible-light irradiation
Fu, Zi-Cheng,Mi, Cheng,Sun, Yan,Yang, Zhi,Xu, Quan-Qing,Fu, Wen-Fu
, (2019/05/27)
We present two as-synthesized Fe(II)-based molecular catalysts with 1,10-phenanthroline (phen) ligands; Fe(phen)3Cl2 (1) and [Fe(phen)2(CH3CH2OH)Cl]Cl (2), and their robust catalytic properties for the conversion of CO2 to CO in DMF/TEOA (DMF = N,N’-dimethylformamide; TEOA = triethanolamine) solution containing Ru(bpy)32+ and BIH (1,3-dimethyl-2-phenyl-2,3-dihydro-1H-benzo-[d]-imidazole). High turnover numbers (TONs) of 19,376 were achieved with turnover frequencies (TOFs) of 3.07 s?1 for complex 1 (1.5 × 10?7 M). A quantum efficiency of 0.38% was observed after 5 h irradiated by 450 nm monochromatic light. The generation rate of CO2 and H2 were tuned by optimizing the experimental conditions, resulting in a high CO selectivity of 90%. The remarkable contribution of the photosensitizer to the total TONCO was found being 19.2% (as shown by tests under similar conditions without catalysts) when BIH was employed as a sacrificial electron donor. The product selectivity in complex 2 reached 95%, and the corresponding TONCO and TOFCO were 33,167 and 4.61 s?1 in the same concentration with complex 1 used as catalyst; respectively. This work provides guidance for future designs of simple, highly efficient and selective molecular catalytic systems that facilitate carbon-neutral solar-to-fuel conversion processes
