Confinement Effects of Metal–Organic Framework on the Formation of Charge-Transfer Tetrathiafulvalene Dimers

Three transition metal coordination polymers (CPs) based on the redox-active dimethyl­thio-tetra­thia­fulvalene-bicarbox­ylate (L) and 1,3-bi­(4-pyridyl)­propane (bpp) ligands, formulated as [MnL­(bpp)]_<i>n</i> (<b>1</b>), [CdL­(bpp)]_<i>n</i> (<b>2</b>), and [Cd₂L­(bpp)₂­(H₂O)­(C₂O₄)_0.5]_<i>n</i>·<i>n</i>(ClO₄)·<i>n</i>(H₂O) (<b>3</b>), are crystallographically characterized. Complexes <b>1</b> and <b>2</b> are isostructural 2-D polymers, and <b>3</b> features an unusual 3-D metal–organic framework (MOF). The 3-D MOF is constructed from tetranuclear cluster nodes built through the μ₂-O bridge of the TTF ligand, which is first found for TTF coordination polymers. It is found that the channel generated by the 3-D MOF exerts a confinement effect on the formation of TTF dimers. The TTF dimers show strong intradimer interaction with partial electron transfer or charge transfer, and hence, the Cd compound <b>3</b> has relatively good photocurrent response property in comparison with that of 2-D Cd compound <b>2</b>

A Cyclic Titanium-Oxo Cluster with a Tetrathiafulvalene Connector as a Precursor for Highly Efficient Adsorbent of Cationic Dyes

Titanium-oxo clusters (TOCs) have been studied for applications in catalysis, energy storage and transfer, light emission, and so on; however, use of TOCs for the selective adsorption of dyes has not yet been reported. Herein, a TOC compound formulated as [Ti6O3(OiPr)14(TTFTC)]4 (1, TTFTC = tetrathiafulvalene-tetracarboxylate) was successfully prepared and crystallographically characterized. Compound 1 has a cyclic structure assembled by four Ti6 clusters and four rodlike TTFTC connectors. Red compound 1 self-condenses to form a black polymeric organic–inorganic hybrid material (denoted as B-1), which was characterized by various techniques. B-1 is an amorphous TiO material that is formed by the irregular condensation of 1 by the removal of alkoxyl groups. B-1 exhibits high dye adsorption efficiency toward cationic dyes with a qe value of 651.3 mg/g at 298 K for methylene blue (MB). Moreover, B-1 can be used to selectively remove MB not only from mixed cationic–anionic dye solutions but also from some mixed cationic dyes, which is related to their structures. Kinetic, isotherm, and thermodynamic studies demonstrated that the pseudo-second-order kinetic model and Freundlich model show a good fit to the experimental data. The adsorption process involves an exothermic and entropy decreasing process. In addition, dye-adsorbed B-1 can be further used as a photocurrent-responsive material. The work opens up a new field for the application of TOCs in the selective adsorption and removal of dyes

Confinement Effects of Metal–Organic Framework on the Formation of Charge-Transfer Tetrathiafulvalene Dimers

Three transition metal coordination polymers (CPs) based on the redox-active dimethyl­thio-tetra­thia­fulvalene-bicarbox­ylate (L) and 1,3-bi­(4-pyridyl)­propane (bpp) ligands, formulated as [MnL­(bpp)]n (1), [CdL­(bpp)]n (2), and [Cd2L­(bpp)2­(H2O)­(C2O4)0.5]n·n(ClO4)·n(H2O) (3), are crystallographically characterized. Complexes 1 and 2 are isostructural 2-D polymers, and 3 features an unusual 3-D metal–organic framework (MOF). The 3-D MOF is constructed from tetranuclear cluster nodes built through the μ2-O bridge of the TTF ligand, which is first found for TTF coordination polymers. It is found that the channel generated by the 3-D MOF exerts a confinement effect on the formation of TTF dimers. The TTF dimers show strong intradimer interaction with partial electron transfer or charge transfer, and hence, the Cd compound 3 has relatively good photocurrent response property in comparison with that of 2-D Cd compound 2

Ligand-to-Ligand Charge Transfer within Metal–Organic Frameworks Based on Manganese Coordination Polymers with Tetrathiafulvalene-Bicarboxylate and Bipyridine Ligands

A systematic study on ligand-to-ligand charge-transfer (LLCT) properties of three closely related metal–organic frameworks (MOFs) is presented. These compounds are formulated as [MnL­(4,4′-bpy)­(H2O)]n·nCH3CN (1), [MnL­(bpe)0.5­(DMF)]n·2nH2O (2), and [MnL­(bpa)­(H2O)]n·2nH2O (3) (L = dimethylthio-tetrathia­fulvalene-bicarboxylate, 4,4′-bpy = 4,4′-bipyridine, bpe = 1,2-bis­(4-pyridyl)­ethene, bpa = 1,2-bis­(4-pyridyl)­ethane). The X-ray single-crystal diffractions show that complexes 1–3 are all two-dimensional (2-D) coordination polymers with different frameworks in crystal lattices. Charge-transfer (CT) interactions within these MOFs are visually apparent in colors and vary according to the conjugated states of the bipyridine ligands (4,4′-bpy, bpe, and bpa). Theoretical calculations show that the charge transfer occurs from ligand L to bipyridine. The intensity of the LLCT is in the order of 2 > 1 > 3 investigated by theoretical calculations and ESR, which indicates that the intensity of CT is related to the bipyridyl conjugated state. Photocurrent responses of these compounds are consequently studied, and the results are in agreement with the intensity of charge transfer and linearly related to the LLCT energy

Confinement Effects of Metal–Organic Framework on the Formation of Charge-Transfer Tetrathiafulvalene Dimers

Three transition metal coordination polymers (CPs) based on the redox-active dimethyl­thio-tetra­thia­fulvalene-bicarbox­ylate (L) and 1,3-bi­(4-pyridyl)­propane (bpp) ligands, formulated as [MnL­(bpp)]_<i>n</i> (<b>1</b>), [CdL­(bpp)]_<i>n</i> (<b>2</b>), and [Cd₂L­(bpp)₂­(H₂O)­(C₂O₄)_0.5]_<i>n</i>·<i>n</i>(ClO₄)·<i>n</i>(H₂O) (<b>3</b>), are crystallographically characterized. Complexes <b>1</b> and <b>2</b> are isostructural 2-D polymers, and <b>3</b> features an unusual 3-D metal–organic framework (MOF). The 3-D MOF is constructed from tetranuclear cluster nodes built through the μ₂-O bridge of the TTF ligand, which is first found for TTF coordination polymers. It is found that the channel generated by the 3-D MOF exerts a confinement effect on the formation of TTF dimers. The TTF dimers show strong intradimer interaction with partial electron transfer or charge transfer, and hence, the Cd compound <b>3</b> has relatively good photocurrent response property in comparison with that of 2-D Cd compound <b>2</b>

A Tetrathiafulvalene-based Bimetal–Organic Framework for a Hybrid Lithium-Ion Capacitor: The Role of Bimetallic Centers in Charge Storage and Stability

Metal–organic frameworks (MOFs) have been found to be promising electrode materials for hybrid lithium-ion capacitors (HLICs) but face challenges due to their low capacity and cycling instability. Here, the first tetrathiafulvalene (TTF)-based bimetallic TTFTB-MnCo-MOF 1 was directly used as the electrode material for lithium-ion batteries, which presents enhanced performance compared with the isomorphic monometallic electrodes. Comprehensive characterizations reveal that Mn(II) in 1 is beneficial to the cycling stability and Co(II) contributes to the high specific capacity. The 1||NMC 622 full cell presents a capacity of 154.9 mAh g–1 at 100 mA g–1 in the 200th cycle. 1||AC HLIC displays a high specific energy of 141.4 Wh kg–1 at a specific power of 0.25 kW kg–1 and stable cycling performance. The remarkable performance, long-term cycling stability, and low self-discharge rate of the device are greater than those of most reported HLICs

Ligand-to-Ligand Charge Transfer within Metal–Organic Frameworks Based on Manganese Coordination Polymers with Tetrathiafulvalene-Bicarboxylate and Bipyridine Ligands

A systematic study on ligand-to-ligand charge-transfer (LLCT) properties of three closely related metal–organic frameworks (MOFs) is presented. These compounds are formulated as [MnL­(4,4′-bpy)­(H₂O)]_<i>n</i>·<i>n</i>CH₃CN (<b>1</b>), [MnL­(bpe)_0.5­(DMF)]_<i>n</i>·2<i>n</i>H₂O (<b>2</b>), and [MnL­(bpa)­(H₂O)]_<i>n</i>·2<i>n</i>H₂O (<b>3</b>) (L = dimethylthio-tetrathia­fulvalene-bicarboxylate, 4,4′-bpy = 4,4′-bipyridine, bpe = 1,2-bis­(4-pyridyl)­ethene, bpa = 1,2-bis­(4-pyridyl)­ethane). The X-ray single-crystal diffractions show that complexes <b>1</b>–<b>3</b> are all two-dimensional (2-D) coordination polymers with different frameworks in crystal lattices. Charge-transfer (CT) interactions within these MOFs are visually apparent in colors and vary according to the conjugated states of the bipyridine ligands (4,4′-bpy, bpe, and bpa). Theoretical calculations show that the charge transfer occurs from ligand L to bipyridine. The intensity of the LLCT is in the order of <b>2</b> > <b>1</b> > <b>3</b> investigated by theoretical calculations and ESR, which indicates that the intensity of CT is related to the bipyridyl conjugated state. Photocurrent responses of these compounds are consequently studied, and the results are in agreement with the intensity of charge transfer and linearly related to the LLCT energy

A Tetrathiafulvalene-based Bimetal–Organic Framework for a Hybrid Lithium-Ion Capacitor: The Role of Bimetallic Centers in Charge Storage and Stability

Metal–organic frameworks (MOFs) have been found to be promising electrode materials for hybrid lithium-ion capacitors (HLICs) but face challenges due to their low capacity and cycling instability. Here, the first tetrathiafulvalene (TTF)-based bimetallic TTFTB-MnCo-MOF 1 was directly used as the electrode material for lithium-ion batteries, which presents enhanced performance compared with the isomorphic monometallic electrodes. Comprehensive characterizations reveal that Mn(II) in 1 is beneficial to the cycling stability and Co(II) contributes to the high specific capacity. The 1||NMC 622 full cell presents a capacity of 154.9 mAh g–1 at 100 mA g–1 in the 200th cycle. 1||AC HLIC displays a high specific energy of 141.4 Wh kg–1 at a specific power of 0.25 kW kg–1 and stable cycling performance. The remarkable performance, long-term cycling stability, and low self-discharge rate of the device are greater than those of most reported HLICs

Confinement Effects of Metal–Organic Framework on the Formation of Charge-Transfer Tetrathiafulvalene Dimers

Three transition metal coordination polymers (CPs) based on the redox-active dimethyl­thio-tetra­thia­fulvalene-bicarbox­ylate (L) and 1,3-bi­(4-pyridyl)­propane (bpp) ligands, formulated as [MnL­(bpp)]_<i>n</i> (<b>1</b>), [CdL­(bpp)]_<i>n</i> (<b>2</b>), and [Cd₂L­(bpp)₂­(H₂O)­(C₂O₄)_0.5]_<i>n</i>·<i>n</i>(ClO₄)·<i>n</i>(H₂O) (<b>3</b>), are crystallographically characterized. Complexes <b>1</b> and <b>2</b> are isostructural 2-D polymers, and <b>3</b> features an unusual 3-D metal–organic framework (MOF). The 3-D MOF is constructed from tetranuclear cluster nodes built through the μ₂-O bridge of the TTF ligand, which is first found for TTF coordination polymers. It is found that the channel generated by the 3-D MOF exerts a confinement effect on the formation of TTF dimers. The TTF dimers show strong intradimer interaction with partial electron transfer or charge transfer, and hence, the Cd compound <b>3</b> has relatively good photocurrent response property in comparison with that of 2-D Cd compound <b>2</b>