Cobalt complexes of the chelating dicarboxylate ligand “esp”: a paddlewheel-type dimer and a heptanuclear coordination cluster

Pakula, Ryan J.; Berry, John F.

doi:10.1039/c8dt03030h

Cited by 20 publications

(12 citation statements)

References 85 publications

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“…For Co, the preferred spin state of each metal cation is high-spin (HS), which involves a local magnetic moment μ = 3 μB per Co(II) cation. This result agrees with the experimental determination by Pakula and Berry, who showed that Co(II) species are in high-spin state in Co paddlewheel units [56], although they found that the local magnetic moments were aligned antiferromagnetically within the paddlewheel, whereas in our calculation we found that the ferromagnetic alignment is more stable. or solvent molecules, e.g.…”

Section: Framework Geometry and Magnetic Ground Statessupporting

confidence: 93%

“…or solvent molecules, e.g. water [53] or ethanol [56]. If we perform our calculation for the Nipaddlewheel system with water molecules added in axial position making each Ni centre pentacoordinated, then we find that the high-spin antiferromagnetic state is the most stable, followed by the high-spin ferromagnetic ground state, which in this case is only 0.06 eV higher in energy.…”

Section: Framework Geometry and Magnetic Ground Statesmentioning

confidence: 91%

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Engineering the electronic and optical properties of 2D porphyrin-paddlewheel metal-organic frameworks

Posligua¹,

Pandya²,

Aziz³

et al. 2021

J. Phys. Energy

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Metal-organic frameworks (MOFs) are promising photocatalytic materials due to their high surface area and tuneability of their electronic structure. We discuss here how to engineer the band structures and optical properties of a family of two-dimensional porphyrin-based MOFs, consisting of M-tetrakis(4-carboxyphenyl)porphyrin structures (M-TCPP, where M = Zn or Co) and metal (Co, Ni, Cu or Zn) paddlewheel clusters, with the aim of optimising their photocatalytic behaviour in solar fuel synthesis reactions (water-splitting and/or CO2 reduction). Based on density functional theory (DFT) and time-dependent DFT simulations with a hybrid functional, we studied three types of composition/structural modifications: (a) varying the metal centre at the paddlewheel or at the porphyrin centre to modify the band alignment; (b) partially reducing the porphyrin unit to chlorin, which leads to stronger absorption of visible light; and (c) substituting the benzene bridging between the porphyrin and paddlewheel, by ethyne or butadiyne bridges, with the aim of modifying the linker to metal charge transfer behaviour. Our work offers new insights on how to improve the photocatalytic behaviour of porphyrin- and paddlewheel-based MOFs.

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Section: Framework Geometry and Magnetic Ground Statessupporting

confidence: 93%

Section: Framework Geometry and Magnetic Ground Statesmentioning

confidence: 91%

Engineering the electronic and optical properties of 2D porphyrin-paddlewheel metal-organic frameworks

Posligua¹,

Pandya²,

Aziz³

et al. 2021

J. Phys. Energy

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“…Two new homobimetallic lantern complexes with carboxylate backbones and the same terminal linker group were synthesized to enable comparison between complexes with S and O donor atoms. These are [Cu 2 (OAc) 4 (pySMe) 2 ] ( 6 ) (OAc = acetate) and [Co 2 (esp) 2 (pySMe) 2 ] ( 7 ) (esp = α,α,α′,α′-tetramethyl-1,3 benzenedipropionate), an analogue of a [Co 2 (esp) 2 (EtOH) 2 ] lantern previously reported. , Synthetic details and characterization are reported in the SI.…”

Section: Methodsmentioning

confidence: 99%

“…These are [Cu 2 (OAc) 4 (pySMe) 2 ] (6) (OAc = acetate) and [Co 2 (esp) 2 (pySMe) 2 ] (7) (esp = α,α,α′,α′-tetramethyl-1,3 benzenedipropionate), an analogue of a [Co 2 (esp) 2 (EtOH) 2 ] lantern previously reported. 64,65 Synthetic details and characterization are reported in the SI.…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

Hard–Soft Chemistry Design Principles for Predictive Assembly of Single Molecule-Metal Junctions

et al. 2021

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The achievement of atomic control over the organic–inorganic interface is key to engineering electronic and spintronic properties of molecular devices. We leverage insights from inorganic chemistry to create hard–soft acid–base (HSAB) theory-derived design principles for incorporation of single molecules onto metal electrodes. A single molecule circuit is assembled via a bond between an organic backbone and an under-coordinated metal atom of the electrode surface, typically Au. Here, we study molecular composition factors affecting the junction assembly of coordination complexes containing transition metals atoms on Au electrodes. We employ hetero- and homobimetallic lantern complexes and systematically change the coordination environment to vary the character of the intramolecular bonds relative to the electrode-molecule interaction. We observe that trends in the robustness and chemical selectivity of single molecule junctions formed with a range of linkers correlate with HSAB principles, which have traditionally been used to guide atomic arrangements in the synthesis of coordination complexes. We find that this similarity between the intermolecular electrode-molecule bonding in a molecular circuit and the intramolecular bonds within a coordination complex has implications for the design of metal-containing complexes compatible with electrical measurements on metal electrodes. Our results here show that HSAB principles determine which intramolecular interactions can be compromised by inter molecule-electrode coordination; in particular on Au electrodes, soft–soft metal–ligand bonding is vulnerable to competition from soft–soft Au-linker bonding in the junction. Neutral donor–acceptor intramolecular bonds can be tuned by the Lewis acidity of the transition metal ion, suggesting future synthetic routes toward incorporation of transition metal atoms into molecular junctions for increased functionality of single molecule devices.

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“…Additionally, it supports four carboxylate bridges. Both contributions generate an AF exchange of J /k B = −9.49 K [ 55 ].…”

Section: Discussionmentioning

confidence: 99%

Slow Magnetic Relaxation in {[CoCxAPy)] 2.15 H2O}n MOF Built from Ladder-Structured 2D Layers with Dimeric SMM Rungs

et al. 2021

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We present the magnetic properties of the metal-organic framework {[CoCxAPy]·2.15 H2O}n (Cx = bis(carboxypropyl)tetramethyldisiloxane; APy = 4,4`-azopyridine) (1) that builds up from the stacking of 2D coordination polymers. The 2D-coordination polymer in the bc plane is formed by the adjacent bonding of [CoCxAPy] 1D two-leg ladders with Co dimer rungs, running parallel to the c-axis. The crystal packing of 2D layers shows the presence of infinite channels running along the c crystallographic axis, which accommodate the disordered solvate molecules. The Co(II) is six-coordinated in a distorted octahedral geometry, where the equatorial plane is occupied by four carboxylate oxygen atoms. Two nitrogen atoms from APy ligands are coordinated in apical positions. The single-ion magnetic anisotropy has been determined by low temperature EPR and magnetization measurements on an isostructural compound {[Zn0.8Co0.2CxAPy]·1.5 CH3OH}n (2). The results show that the Co(II) ion has orthorhombic anisotropy with the hard-axis direction in the C2V main axis, lying the easy axis in the distorted octahedron equatorial plane, as predicted by the ab initio calculations of the g-tensor. Magnetic and heat capacity properties at very low temperatures are rationalized within a S* = 1/2 magnetic dimer model with anisotropic antiferromagnetic interaction. The magnetic dimer exhibits slow relaxation of the magnetization (SMM) below 6 K in applied field, with a tlf ≈ 2 s direct process at low frequencies, and an Orbach process at higher frequencies with U/kB = 6.7 ± 0.5 K. This compound represents a singular SMM MOF built-up of Co-dimers with an anisotropic exchange interaction.

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Cobalt complexes of the chelating dicarboxylate ligand “esp”: a paddlewheel-type dimer and a heptanuclear coordination cluster

Cited by 20 publications

References 85 publications

Engineering the electronic and optical properties of 2D porphyrin-paddlewheel metal-organic frameworks

Engineering the electronic and optical properties of 2D porphyrin-paddlewheel metal-organic frameworks

Hard–Soft Chemistry Design Principles for Predictive Assembly of Single Molecule-Metal Junctions

Slow Magnetic Relaxation in {[CoCxAPy)] 2.15 H2O}n MOF Built from Ladder-Structured 2D Layers with Dimeric SMM Rungs

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