DFT Study of Acceptorless Alcohol Dehydrogenation Mediated by Ruthenium Pincer Complexes: Ligand Tautomerization Governing Metal Ligand Cooperation

Metal ligand cooperation (MLC) catalysis is a popular strategy to design highly efficient transition metal catalysts. In this presented theoretical study, we describe the key governing factor in the MLC mechanism, with the Szymczak’s NNN-Ru and the Milstein’s PNN-Ru complexes as two representative catalysts. Both the outer-sphere and inner-sphere mechanisms were investigated and compared. Our calculated result indicates that the PNN-Ru pincer catalyst will be restored to aromatic state during the catalytic cycle, which can be considered as the driving force to promote the MLC process. On the contrary, for the NNN-Ru catalyst, the MLC mechanism leads to an unfavored tautomerization in the pincer ligand, which explains the failure of the MLC mechanism in this system. Therefore, the strength of the driving force provided by the pincer ligand actually represents a prerequisite factor for MLC. Spectator ligands such as CO, PPh₃, and hydride are important to ensure the catalyst follow a certain mechanism as well. We also evaluate the driving force of various bifunctional ligands by computational methods. Some proposed pincer ligands may have the potential to be the new pincer catalysts candidates. The presented study is expected to offer new insights for MLC catalysis and provide useful guideline for future catalyst design

Achieving <i>In Situ</i> Dynamic Fluorescence in the Solid State through Synergizing Cavities of Macrocycle and Channels of Framework

To achieve in situ dynamic fluorescence in the solid state and unveil the mechanism remain a formidable challenge. Herein, through synergizing the cavities of macrocycles for dynamic complexing and the channels of frameworks for facile transit, we construct intrinsic channels from an emissive cyclophane and realize precisely tunable emission in the solid state through the sequential guests’ exchange. Specifically, two design criteria involve (1) The twisted cyanostilbene units not only endow the systems with solid-state fluorescence but also tailor the π–π interactions in the complex to generate the desired emission and (2) the large cavity of cyclophane results in the formation of ternary complexes with controllable binding affinity which further assemble into robust channels for the guests’ exchange in the bulky state. This strategy unifies the advantages of both macrocycle and framework in one system, achieving visualization, recyclability, and easy processability simultaneously. The present study paves an easy, efficient, and general platform for constructing dynamic optical materials

Achieving <i>In Situ</i> Dynamic Fluorescence in the Solid State through Synergizing Cavities of Macrocycle and Channels of Framework

To achieve in situ dynamic fluorescence in the solid state and unveil the mechanism remain a formidable challenge. Herein, through synergizing the cavities of macrocycles for dynamic complexing and the channels of frameworks for facile transit, we construct intrinsic channels from an emissive cyclophane and realize precisely tunable emission in the solid state through the sequential guests’ exchange. Specifically, two design criteria involve (1) The twisted cyanostilbene units not only endow the systems with solid-state fluorescence but also tailor the π–π interactions in the complex to generate the desired emission and (2) the large cavity of cyclophane results in the formation of ternary complexes with controllable binding affinity which further assemble into robust channels for the guests’ exchange in the bulky state. This strategy unifies the advantages of both macrocycle and framework in one system, achieving visualization, recyclability, and easy processability simultaneously. The present study paves an easy, efficient, and general platform for constructing dynamic optical materials

Achieving <i>In Situ</i> Dynamic Fluorescence in the Solid State through Synergizing Cavities of Macrocycle and Channels of Framework

To achieve in situ dynamic fluorescence in the solid state and unveil the mechanism remain a formidable challenge. Herein, through synergizing the cavities of macrocycles for dynamic complexing and the channels of frameworks for facile transit, we construct intrinsic channels from an emissive cyclophane and realize precisely tunable emission in the solid state through the sequential guests’ exchange. Specifically, two design criteria involve (1) The twisted cyanostilbene units not only endow the systems with solid-state fluorescence but also tailor the π–π interactions in the complex to generate the desired emission and (2) the large cavity of cyclophane results in the formation of ternary complexes with controllable binding affinity which further assemble into robust channels for the guests’ exchange in the bulky state. This strategy unifies the advantages of both macrocycle and framework in one system, achieving visualization, recyclability, and easy processability simultaneously. The present study paves an easy, efficient, and general platform for constructing dynamic optical materials

Achieving <i>In Situ</i> Dynamic Fluorescence in the Solid State through Synergizing Cavities of Macrocycle and Channels of Framework

To achieve in situ dynamic fluorescence in the solid state and unveil the mechanism remain a formidable challenge. Herein, through synergizing the cavities of macrocycles for dynamic complexing and the channels of frameworks for facile transit, we construct intrinsic channels from an emissive cyclophane and realize precisely tunable emission in the solid state through the sequential guests’ exchange. Specifically, two design criteria involve (1) The twisted cyanostilbene units not only endow the systems with solid-state fluorescence but also tailor the π–π interactions in the complex to generate the desired emission and (2) the large cavity of cyclophane results in the formation of ternary complexes with controllable binding affinity which further assemble into robust channels for the guests’ exchange in the bulky state. This strategy unifies the advantages of both macrocycle and framework in one system, achieving visualization, recyclability, and easy processability simultaneously. The present study paves an easy, efficient, and general platform for constructing dynamic optical materials

Achieving <i>In Situ</i> Dynamic Fluorescence in the Solid State through Synergizing Cavities of Macrocycle and Channels of Framework

To achieve in situ dynamic fluorescence in the solid state and unveil the mechanism remain a formidable challenge. Herein, through synergizing the cavities of macrocycles for dynamic complexing and the channels of frameworks for facile transit, we construct intrinsic channels from an emissive cyclophane and realize precisely tunable emission in the solid state through the sequential guests’ exchange. Specifically, two design criteria involve (1) The twisted cyanostilbene units not only endow the systems with solid-state fluorescence but also tailor the π–π interactions in the complex to generate the desired emission and (2) the large cavity of cyclophane results in the formation of ternary complexes with controllable binding affinity which further assemble into robust channels for the guests’ exchange in the bulky state. This strategy unifies the advantages of both macrocycle and framework in one system, achieving visualization, recyclability, and easy processability simultaneously. The present study paves an easy, efficient, and general platform for constructing dynamic optical materials

Achieving <i>In Situ</i> Dynamic Fluorescence in the Solid State through Synergizing Cavities of Macrocycle and Channels of Framework

To achieve in situ dynamic fluorescence in the solid state and unveil the mechanism remain a formidable challenge. Herein, through synergizing the cavities of macrocycles for dynamic complexing and the channels of frameworks for facile transit, we construct intrinsic channels from an emissive cyclophane and realize precisely tunable emission in the solid state through the sequential guests’ exchange. Specifically, two design criteria involve (1) The twisted cyanostilbene units not only endow the systems with solid-state fluorescence but also tailor the π–π interactions in the complex to generate the desired emission and (2) the large cavity of cyclophane results in the formation of ternary complexes with controllable binding affinity which further assemble into robust channels for the guests’ exchange in the bulky state. This strategy unifies the advantages of both macrocycle and framework in one system, achieving visualization, recyclability, and easy processability simultaneously. The present study paves an easy, efficient, and general platform for constructing dynamic optical materials

Achieving <i>In Situ</i> Dynamic Fluorescence in the Solid State through Synergizing Cavities of Macrocycle and Channels of Framework

To achieve in situ dynamic fluorescence in the solid state and unveil the mechanism remain a formidable challenge. Herein, through synergizing the cavities of macrocycles for dynamic complexing and the channels of frameworks for facile transit, we construct intrinsic channels from an emissive cyclophane and realize precisely tunable emission in the solid state through the sequential guests’ exchange. Specifically, two design criteria involve (1) The twisted cyanostilbene units not only endow the systems with solid-state fluorescence but also tailor the π–π interactions in the complex to generate the desired emission and (2) the large cavity of cyclophane results in the formation of ternary complexes with controllable binding affinity which further assemble into robust channels for the guests’ exchange in the bulky state. This strategy unifies the advantages of both macrocycle and framework in one system, achieving visualization, recyclability, and easy processability simultaneously. The present study paves an easy, efficient, and general platform for constructing dynamic optical materials

Achieving <i>In Situ</i> Dynamic Fluorescence in the Solid State through Synergizing Cavities of Macrocycle and Channels of Framework

To achieve in situ dynamic fluorescence in the solid state and unveil the mechanism remain a formidable challenge. Herein, through synergizing the cavities of macrocycles for dynamic complexing and the channels of frameworks for facile transit, we construct intrinsic channels from an emissive cyclophane and realize precisely tunable emission in the solid state through the sequential guests’ exchange. Specifically, two design criteria involve (1) The twisted cyanostilbene units not only endow the systems with solid-state fluorescence but also tailor the π–π interactions in the complex to generate the desired emission and (2) the large cavity of cyclophane results in the formation of ternary complexes with controllable binding affinity which further assemble into robust channels for the guests’ exchange in the bulky state. This strategy unifies the advantages of both macrocycle and framework in one system, achieving visualization, recyclability, and easy processability simultaneously. The present study paves an easy, efficient, and general platform for constructing dynamic optical materials

Hydrogenation of Carbon Dioxide Using Half-Sandwich Cobalt, Rhodium, and Iridium Complexes: DFT Study on the Mechanism and Metal Effect

The hydrogenation of carbon dioxide catalyzed by half-sandwich transition metal complexes (M = Co, Rh, and Ir) was studied systematically through density functional theory calculations. All metal complexes are found to process a similar mechanism, which involves two main steps, the heterolytic cleavage of H₂ and the hydride transfer. The heterolytic cleavage of H₂ is the rate-determining step. The comparison of three catalytic systems suggests that the Ir catalyst has the lowest activation free energy (13.4 kcal/mol). In contrast, Rh (14.2 kcal/mol) and Co (18.3 kcal/mol) catalysts have to overcome relatively higher free energy barriers. The different catalytic efficiency of Co, Rh, and Ir is attributed to the back-donation ability of different metal centers, which significantly affects the H₂ heterolytic cleavage. The highest activity of an iridium catalyst is attributed to its strong back-donation ability, which is described quantitatively by the second order perturbation theory analysis. Our study indicates that the functional group of the catalyst plays versatile roles on the catalytic cycle to facilitate the reaction. It acts as a base (deprotonated) to assist the heterolytic cleavage of H₂. On the other hand, during the hydride transfer, it can also serve as Brønsted acid (protonated) to lower the LUMO of CO₂. This ligand assisted pathway is more favorable than the direct attack of hydride to CO₂. These finds highlight that the unique features of the metal center and the functional ligands are crucial for the catalyst design in the hydrogenation of carbon dioxide