•Hybrid systems built by integration of the first-row transition metal complexes with inorganic or organic semiconductors for photocatalytic H2 production are surveyed in the review.•The review also ...includes the photocatalytic H2 production hybrid systems containing an organometallic complex and an inorganic or organic nanomaterial as well as a metal-organic framework (MOF) material.•The mechanisms for the light-driven H2-generation reactions catalyzed by the hybrid systems are presented.
The development of energy-efficient, cost-effective and durable photocatalytic systems for water splitting is one of the scientific problems that must be solved before the successful transformation from a fossil fuel-based economy to a solar fuel-based economy can be realized. Conventional photocatalytic systems are generally divided into heterogeneous systems of semiconductors, usually modified by noble metals or inorganic cocatalysts, and homogeneous systems comprised of molecular catalysts and organic or organometallic chromophores. In recent years, some hybrid photocatalytic systems were reported to be highly active and robust for photoinduced H2 production, indicating that the integration of semiconducting materials with proper molecular catalysts is an effective strategy for constructing efficient photocatalytic systems for water splitting. This review will focus on hybrid photocatalytic systems, developed in the past three years, in which proton reduction molecular catalysts incorporate either semiconducting materials or inorganic, metal-organic, and other polymeric nanomaterials for photochemical H2 generation from water. In the last section of the review, problems existing in the current hybrid photocatalytic systems are discussed; future challenges and developments are envisaged.
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•A highly efficient molecular SAC has been found whose nitrogen reduction efficiency is comparable to other known SACs.•CrCp and MnBz have extremely low limiting potentials of −0.29 V ...and −0.37 V, respectively.•In-depth research on the reaction mechanism found that the local magnetic moment plays a key role in the activation of nitrogen.•The descriptor of ΔE(*N2H) was discovered, and the mechanism was further investigated.
The coordination environment of metal atoms in single-atom catalysts (SACs) has a greater impact on the catalytic performance of electrocatalysts. However, the influence mechanism of interacting ligands on the electrocatalytic nitrogen reduction reaction (NRR) process is still insufficient. Herein, by means of large-scale density functional theory (DFT) computations, the effect of organic ligands on the NRR process is investigated in-depth using half organometallic sandwich molecular SACs, i.e. TMBzs and TMCps (Bz = benzene, Cp = cyclopentadienyl, and TM = transition metal). The results revealed that the NRR performance of all the systems is highly dependent on the choice of d-π interaction within the TM-Ligand complexes. Compared with TMBzs, the TMCps exhibit outstanding NRR activity and significantly suppress HER. Among 16 candidates, CrCp and MnBz are the most promising candidates with an ultra-low limiting potential of −0.29 V and −0.37 V via consecutive mechanism, respectively. Moreover, the systems with higher spin polarizations have better NRR activity. The work provides new insight into the NRR to molecular SACs with different organic ligands.
Pincer ligands and their metal complexes are ubiquitous in coordination and organometallic chemistry owing to the unusual properties they impart on the metal centers to which they are coordinated. ...They have wide ranging applications and this review explores various categories of pincer ligands and the metal complexes.
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Pincer ligands continue to generate interest owing to the unusual properties they impart on metal centers and consequently on the complexes they are involved in. These ligands and their metal complexes have aided in the understanding of a number of processes mediated by organometallic and non-organometallic systems. In homogenous catalytic transformations, pincer ligands provide enhanced chemical and thermal stability which serve to minimize the leaching of the metal during the catalytic cycle. These ligands also offer the ability to fine tune the electronic and the steric properties about the metal center, thereby increasing the scope of their applications. This review discusses some of the general synthetic protocols of the main classes of pincer ligands with a focus on some of their more popular applications.
Transition metal catalysis has traditionally relied on organometallic complexes that can cycle through a series of ground-state oxidation levels to achieve a series of discrete yet fundamental ...fragment-coupling steps. The viability of excited-state organometallic catalysis via direct photoexcitation has been demonstrated. Although the utility of triplet sensitization by energy transfer has long been known as a powerful activation mode in organic photochemistry, it is surprising to recognize that photosensitization mechanisms to access excited-state organometallic catalysts have lagged far behind. Here, we demonstrate excited-state organometallic catalysis via such an activation pathway: Energy transfer from an iridium sensitizer produces an excited-state nickel complex that couples aryl halides with carboxylic acids. Detailed mechanistic studies confirm the role of photosensitization via energy transfer.
Organometallic complexes (OMCs) have shown promising properties in improving battery performance. Different OMCs and in-depth analyses of their structure-performance relationships are reviewed. ...Future perspectives on the opportunities and challenges of OMCs are provided.
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•Applications of organometallic complexes in batteries are reviewed.•In-depth analyses of structure-performance relationships are provided.•Strategies of improving battery performance are discussed in detail.•The future research and development of OMCs for batteries are prospected.
Organometallic complexes (OMCs) consisting of organic and metal active moieties have shown immense potential for application in batteries. The diverse structure, rich porosity, and unique charge centers of OMCs enable them to be functional in batteries. In this review, we first classify OMCs into metal-organic frameworks, porphyrin, phthalocyanine, and ferrocene etc. Then, we mainly focus on the recent progress of each type of OMCs in rechargeable batteries. They can serve as electrode or electrolyte materials in a variety of battery systems such as Li, Na, Zn, Li-S, Li-O2, and redox flow batteries. The performance enhancements in these batteries are closely related to the structures and properties of OMCs. In-depth analyses of the structure-performance relationships is provided. At the end, perspectives on the opportunities and challenges of these materials are given. This review would endow more inspiration on the development of OMCs for advanced batteries.
The formation of carbon-nitrogen bonds for the preparation of aromatic amines is among the top five reactions carried out globally for the production of high-value materials, ranging from from bulk ...chemicals to pharmaceuticals and polymers. As a result of this ubiquity and diversity, methods for their preparation impact the full spectrum of chemical syntheses in academia and industry. In general, these molecules are assembled through the stepwise introduction of a reactivity handle in place of an aromatic C-H bond (that is, a nitro group, halogen or boronic acid) and a subsequent functionalization or cross-coupling. Here we show that aromatic amines can be constructed by direct reaction of arenes and alkyl amines using photocatalysis, without the need for pre-functionalization. The process enables the easy preparation of advanced building blocks, tolerates a broad range of functionalities, and multigram scale can be achieved via a batch-to-flow protocol. The merit of this strategy as a late-stage functionalization platform has been demonstrated by the modification of several drugs, agrochemicals, peptides, chiral catalysts, polymers and organometallic complexes.
Chemical doping is a key process for investigating charge transport in organic semiconductors and improving certain (opto)electronic devices
. N(electron)-doping is fundamentally more challenging ...than p(hole)-doping and typically achieves a very low doping efficiency (η) of less than 10%
. An efficient molecular n-dopant should simultaneously exhibit a high reducing power and air stability for broad applicability
, which is very challenging. Here we show a general concept of catalysed n-doping of organic semiconductors using air-stable precursor-type molecular dopants. Incorporation of a transition metal (for example, Pt, Au, Pd) as vapour-deposited nanoparticles or solution-processable organometallic complexes (for example, Pd
(dba)
) catalyses the reaction, as assessed by experimental and theoretical evidence, enabling greatly increased η in a much shorter doping time and high electrical conductivities (above 100 S cm
; ref.
). This methodology has technological implications for realizing improved semiconductor devices and offers a broad exploration space of ternary systems comprising catalysts, molecular dopants and semiconductors, thus opening new opportunities in n-doping research and applications
.
The development of energy-efficient, cost-effective and durable photocatalytic systems for water splitting is one of the scientific problems that must be solved before the successful transformation ...from a fossil fuel-based economy to a solar fuel-based economy can be realized. Conventional photocatalytic systems are generally divided into heterogeneous systems of semiconductors, usually modified by noble metals or inorganic cocatalysts, and homogeneous systems comprised of molecular catalysts and organic or organometallic chromophores. In recent years, some hybrid photocatalytic systems were reported to be highly active and robust for photoinduced H-2 production, indicating that the integration of semiconducting materials with proper molecular catalysts is an effective strategy for constructing efficient photocatalytic systems for water splitting. This review will focus on hybrid photocatalytic systems, developed in the past three years, in which proton reduction molecular catalysts incorporate either semiconducting materials or inorganic, metal-organic, and other polymeric nanomaterials for photochemical H-2 generation from water. In the last section of the review, problems existing in the current hybrid photocatalytic systems are discussed; future challenges and developments are envisaged.
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•Ruthenium N-heterocyclic carbenes are active catalysts for hydrogenation reactions.•Transfer and direct hydrogenation are covered, comprising asymmetric reductions.•Reduced ...substrates include ketones, aldehydes, olefins, nitriles, imines and esters.•Catalyst properties are easily tuned by varying wingtip and backbone substituents.•Inner and outer sphere mechanism can be evidenced, depending on the catalyst.
This review provides a brief overview of advances on ruthenium(II) N-heterocyclic carbene complexes (NHCs) applied for hydrogenation reactions undertaken during the last five years. Several structural motifs, containing mono-, bi-, tri- and tetradentate binding modes of the NHCs are discussed in combination with a variety of different wingtip substituents to provide active catalysts for hydrogenation reactions. While bidentate ligands afford the more active catalysts than their monodentate analogues, pincer ligands must be chosen carefully to enable the formation of a free coordination site in catalysis. Transfer hydrogenation and direct hydrogenation of ketones and aldehydes, olefins, nitriles, imines and esters are summarized, showing the trend towards hydrogen transfer from other sources than hydrogen gas. Recently developed chiral NHCs offer the opportunity for asymmetric transformations as a possible pathway to access natural products.
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