Electrically conductive 1D coordination polymers: design strategies and controlling factors

1D p-type molecular-based coordination polymer semiconductor with ultrahigh mobility

One-dimensional (1D) semiconductor nanostructures exhibit exceptional performance in mitigating short-channel effects and ensuring low power consumption. However, the scarcity of high-mobility p-type 1D materials impedes further advancement. Molecular-based materials offer high designability in structure and properties, making them a promising candidate for 1D p-type semiconductor materials. A molecular-based 1D p-type material was developed under the guidance of coordination chemistry. Cu-HT (HT is the abbreviation of p-hydroxy thiophenol) combines the merits of highly orbital overlap between Cu and S, fully covered surface modification with phenol functional groups, and unique cuprophilic (Cu-Cu) interactions. As such, Cu-HT has a remarkable hole mobility of 27.2 cm2 V-1 s-1, which is one of the highest reported values for 1D molecular-based materials to date and even surpass those of commonly used amorphous silicon as well as the majority of 1D inorganic materials. This achievement underscores the significant potential of coordination polymers in optimizing carrier transport and represents a major advancement in the synthesis of high-performance, 1D p-type semiconductor materials.

Diamondoid Ni(II) Coordination Polymer as an Electrocatalyst for Hydrogen and Oxygen Evolution Reactions and Overall Water Splitting

We have successfully synthesized a new Ni(II)-based coordination polymer (CP) [Ni2(cis-1,4-chdc)2(4,4'-bpy)3(H2O)2] (1); (cis-1,4- H2chdc=cis-1,4-cyclohexanedicarboxylic acid and 4,4'-bpy=4,4'-bipyridine) employing slow diffusion method in a single pot technique. The connectivity of Ni(II) ions and bridging cis-1,4-chdc ligand gives rise to a three-dimensional (3D) framework with 2-fold interpenetrated diamondoid topology. Interestingly, the synthesized CP acts as efficient catalyst for electrocatalytic water splitting. The water oxidation activity of compound 1 exhibits Tafel slope equivalent to 361.48 mV.dec-1 for hydrogen evolution reaction (HER) and 353.53 mV.dec-1 for oxygen evolution reaction (OER) in an alkaline medium while almost similar values of Tafel slope for HER and OER equivalent to 287.33 mV.dec-1 and 289.93 mV.dec-1 respectively in acidic medium. Thus, the compound 1 has excellent efficacy in catalyzing HER and OER in acidic as well as alkaline medium, which is ascribed to its distinctive 3D architecture.

Application of a distinctly bent, trinuclear, end-to-end azide bridged, mixed valence cobalt(iii/ii/iii) complex in the fabrication of photosensitive Schottky barrier diodes

A mixed-valence trinuclear cobalt(iii)-cobalt(ii)-cobalt(iii) complex, [(μ-1,3-N3)Co3L(N3)3]·MeOH has been synthesized using a tetradentate N2O2 donor 'reduced Schiff base' ligand, H2L {1,3-bis(2-hydroxybenzylamino)2,2-dimethylpropane} and azide as anionic co-ligand. The complex has been characterised by elemental analysis, IR, UV-vis spectroscopy and single-crystal X-ray diffraction studies etc. The cobalt(iii)-cobalt(ii)-cobalt(iii) skeleton in the complex is non-linear and non-centrosymmetric. The redox behavior of the complex was studied by using Cyclic Voltammetry (CV). The complex is found to be a semiconductor material as confirmed by determining the band gap of this complex by experimental as well as theoretical studies. The band gap in the solid state has been determined experimentally. The conductivity of the synthesized complex based device improves considerably in illumination conditions from the non-illuminated conditions. The complex has also been used to fabricate Schottky barrier diodes.

Solvent-induced structural transformation in a one-dimensional coordination polymer

We have rationally designed a one-dimensional coordination polymer (1D CP), termed 1D-DGIST-18, that exhibits intrinsic structural flexibility. This 1D CP enables its expansion into a three-dimensional network through supramolecular interactions involving coordinated solvents and/or ligands. The strategic selection of solvents for solvent exchange, prior to drying, significantly influences the structures of 1D-DGIST-18 by removing certain coordinating solvents and modulating π-π stacking. Consequently, a hierarchical porosity emerges, ranging from micro- to meso- to macroporous structures, which is attributed to its inherent structural dynamics. Additionally, the formation of excimers endows 1D-DGIST-18, when immersed in acetone, with 'turn-on' fluorescence, as evidenced by fluorescence decay profiles. These structural transitions within 1D-DGIST-18 are further elucidated using single-crystal X-ray diffractometry. The insights from this study provide a foundation for the design of materials with structural dynamics and tunable properties.

Correlation in Structural Architecture toward Fabrication of Schottky Device with a Series of Pyrazine Appended Coordination Polymers

Energy is the center of importance for the survivability of civilization. Use of fossil fuel is going to be suspended, and renewable energy is technologically costlier. In the quest for new energy sources and to minimize fuel expenditure, the design of energy efficient devices is one of the solutions. Toward this objective, highly delocalized π-acidic N-hetreocycle pyrazine bridged Cd(II)-based coordination polymers (CPs), [Cd(tppz)(adc)(MeOH)] (1), [Cd(tppz)(trep)] (2), and [Cd(tppz)(2,6-ndc)] (3; tppz = 2,3,5,6-tetrakis(2-pyridyl)pyrazine) are synthesized in combination with π-accessible dicarboxylato linkers (acetylene dicarboxylic acid (H2adc), terephthalic acid (H2trep), and 2,6-naphthalene dicarboxylic acid (2,6 H2ndc)). The structures of the compounds, 1-3, have been confirmed by single-crystal X-ray diffraction measurements. Analysis of electrical property demonstrates that light irradiation enhances the conductivity and follows the order 3 > 2 > 1; compound 3 possesses the highest conductivity (1.93 × 10-3 (light), 1.12 × 10-4 S m-1 dark)), than 2 (1.80 × 10-4 (light), 1.10 × 10-4 S m-1 (dark)) and 1 (5.06 × 10-5 (light), 4.72 × 10-5 S m-1 (dark)). This light-induced electrical conductivity can pave the way toward fabrication of an active electronic device by using the discussed materials.

Coordination polymers: a promising candidate for photo-responsive electronic device application

The design and synthesis of electrically conductive coordination polymers (CPs) are of special interest due to their applications in the fabrication of many environmentally benign emerging technologies, such as molecular wires, photovoltaic cells, light emitting diodes (LEDs), field effect transistors (FETs) and Schottky barrier diodes (SBDs). Owing to their structural flexibility, easy functionality and adjustable energy levels, CPs are promising candidates for providing a better pathway for superior charge transport. Again, the utilization of visible light as an external stimulus to control and manoeuvre the electrical properties of the CPs is exceptionally motivating for the development of many optoelectronic devices, such as photodetectors, photo-switches, photodiodes and chemiresistive sensors. The applications of such materials in devices will solve questions regarding the energy crisis and environmental concerns. This study provides an overview of the recent advances in the development of photo-responsive CPs and the possibility of their application in developing optoelectronic devices. In this regard, a thorough literature survey was performed and the studies related to the fabrication of photosensitive conducting CPs for applications in optoelectronic devices are listed.

In Situ Oxidation of Pyridyl-Dihydrobenzoimidazoquinazoline and the Synthesis of a Highly Luminescent Cd(II) Coordination Polymer: A Promising Candidate for Mutagenic Nitroaromatic Detection and Device Fabrication

Pyridyl-substituted imidazoquinoline, a potent fluorescent framework, is advantageous to architect multifunctional coordination networks for sensing and fabricating emergent electrical conductors. In this work, a Cd(II)-based one-dimensional (1D) coordination polymer (1D CP), [Cd(glu)2(pbiq)2(H2O)]n (1), [H2glu = glutaric acid and pbiq = 4-(6-(pyridin-4-yl)benzo[4,5]imidazo[1,2-c]quinazoline)], has been structurally confirmed by single-crystal X-ray crystallography. The H-bonding and π···π interactions built a three-dimensional (3D) supramolecular structure that strongly emits at 416 nm in acetonitrile suspension. Potentially intrusive nitroaromatics (NAs) and trinitrophenol (TNP) selectively quench the strong emission of 1, and the highest quenching is noted in the case of TNP. A detection limit (limit of detection (LOD)) of 1.51 × 10-7 M for TNP is determined. The band gap (3.31 eV) of 1 recognizes semiconducting behavior, and an electronic device is fabricated. The correlation of current vs voltage (I-V plot) reveals a substantial non-ohmic electrical conductivity of 1 (Λ: 1.10 × 10-5 S m-1) along with a low energy barrier (ΦB: 0.69), and the series resistance (Rs) becomes 6.21 kΩ.

The Electronic Properties of Cadmium Naphthalene Diimide Coordination Complex

The computational simulations for electronic properties of cadmium (Cd) coordinated L-alanine NDI ligand (H₂-l-ala NDI) based complex are the focus of this research. For the first time, the Cd-NDI complex (monomer) has been produced using water as the solvent; this is a new approach to synthesizing the Cd-NDI complex that has not been reported yet. Along with crystallography and Hirsch field analysis, CAM-B3LYP/LANL2DZ and B3LYP/LANL2MB basis sets were used, and in-depth characterisation of the Cd-NDI complex by following DFT and TD-DFT hypothetical simulations. Hyperpolarizabilities, frontier molecular orbitals (FMOs), the density of states (DOS), dipole moment (µ), electron density distribution map (EDDM), transition density matrix (TDM), molecular electrostatic potential (MEP), electron-hole analysis (EHA), and electrical conductivity (σ) have all been studied regarding the Cd-NDI complex. The vibrational frequencies and types of interaction are studied using infrared (IR) and non-covalent interaction (NCI) analysis with iso-surface. In comparison to the Cd-NDI complex with 2.61, 2.42 eV E_g (using CAM-B3LYP/LANL2DZ and B3LYP/LANL2MB basis sets, respectively) and 376 nm λ_max, (in case of B3LYP/LANL2MB λ_max is higher), H₂-l-ala NDI have 3.387 eV E_g and 375 nm λ_max, metal-ligand coordination in complex dramatically altered charge transfer properties, such as narrowing band gap (E_g). Based on the electronic properties analysis of Cd-NDI complex, it is predicted that the Cd-NDI complex will have a spectacular (nonlinear optical) NLO response. The Cd-NDI complex is discovered to be advantageous for the creation of future nanoscale devices due to the harmony between the Cd metal and H₂-l-ala NDI, in addition to their influences on NLO characteristics.

Cu(II)-Based Molecular Hexagons Forming Honeycomb-like Networks Exhibit High Electrical Conductivity

Four new Cu(II)-based hexagonal complexes with the metallomacrocycle formulae [Cu₆(5-nip)₆(3-py)₆(H₂O)₁₂] (1), [Cu₆(5-nip)₆(3-Clpy)₆(H₂O)₁₂] (2), [Cu₆(5-nip)₆(3-Brpy)₆(H₂O)₁₂] (3), and [Cu₆(5-nip)₆(3-Ipy)₆(H₂O)₁₂] (4) have been synthesized using 5-nitroisophthalic acid (H₂5-nip) and pyridine (py)/3-halopyridine (3-Xpy; X = Cl, Br, and I) ligands. The structural features and supramolecular interactions of compounds 1-4 have been investigated using the single-crystal X-ray diffraction (SCXRD) technique. Interestingly, the hexagonal complexes undergo hydrogen bonding and π···π stacking interactions to form fascinating two-dimensional (2D) honeycomb-like structures. The synthesized complexes exhibit high electrical conductivity, arising from charge transport through space via π···π contacts. However, complexes containing 3-Brpy (3) and 3-Ipy (4) exhibit photosensitivity due to the presence of halogens with a larger size and lower ionization energy. The conductivity results are also in accordance with the theoretical prediction calculated by density functional theory (DFT) study.

Rational synthesis of a pyridyl-imidazoquinazoline based multifunctional 3D Zn(II)-MOF: structure, luminescence, selective and sensitive detection of Al3+ and TNP, and its semiconducting device application

In the age of sustainable development, the exploration of multifunctional materials is of high priority due to their economic benefits and environmental suitability. A stable luminescent coordination polymer, [Zn₂(tdc)₄(pdiq)₃] (1), (pdiq = pyridyl-imidazoquinazoline; H₂tdc = 2,5-thiophenedicarboxylic acid) has been prepared and structurally confirmed by single-crystal X-ray diffraction analysis. The 3D framework consists of a distorted octahedral geometry with a ZnO₄N₂ coordination sphere where four carboxylato-O donations come from two tdc^2- as bridging ligands and two pyridyl-Ns come from two pdiq. The π⋯π interactions between the imidazolium and phenyl groups bestow robustness on the architecture. The compound is chemically stable to water, shows tolerance to acid/base aqueous solutions (pH = 2-12), and is stable to the impact of organic solvents. The high dispersibility of Zn-MOF (1) in acetonitrile may enhance the fluorescence intensity compared to that in water, which prompted fluorescence measurements in the former solvent and it is used for the efficient and selective turn-off ratiometric sensing of Al³⁺ ions (LOD, 1.39 × 10^-7 M). In addition, the fluorescence emission of 1 is instantly quenched by trinitrophenol (TNP) and the LOD is 1.54 × 10^-7 M. The Tauc's plot is used to measure the semiconducting band gap (3.33 eV) and the electrical conductivity is significantly increased upon illumination (Λ: 1.14 × 10^-3 S m^-1 (dark), 5.35 × 10^-3 S m^-1 (light)) and the energy barrier declines marginally (FB: 0.57 (dark), 0.49 (light)). Transit time (τ) and diffusion length (L_D) at the quasi-Fermi level were analyzed to offer information on the charge transport mechanism of the compound. The better performance on photo-irradiation signifies the enhanced charge transfer kinetics of a Zn-MOF coated thin-film device (TFD 1), which encourages its application in semiconductor devices.

A Dual Functional 2D MOF Exhibiting Rare Photosalient Effect as well as Selective Pd(II) Sensing in Aqueous Medium

A Zn(II) based two-dimensional metal-organic framework (2D MOF) [Zn₂(suc)₂(4-nvp)₂] (1) [H₂suc = succinic acid and 4-nvp = 4-(1-naphthylvinyl)pyridine] exhibits a "photosalient effect" under UV light as well as sunlight along with the release of a stereoselective cyclobutane ligand, 1,3-bis(4'-pyridyl)-2,4-bis(naphthyl)cyclobutane (rctt-4-pncb). Photolysis of in situ generated MOF in solution also leads to the formation of rctt-4-pncb crystals. Interestingly, compound 1 shows a high selectivity for Pd(II) sensing in aqueous medium.

Amide-Driven Secondary Building Unit Structural Transformations between Zn(II) Coordination Polymers

The behavior of coordination polymers (CPs) against external stimuli has witnessed remarkable attention, especially when the resulting CPs present reversible molecular arrays. Accordingly, CPs with these characteristics can lead to differences in their properties owing to these structural differences, being promising for their use as potential molecular switches with diverse applications. Herein, we have synthesized four Zn(II) CPs bearing α-acetamidocinnamic acid (HACA) and 4,4'-bipyridine (4,4'-bipy). The reaction between Zn(OAc)₂·2H₂O, HACA, and 4,4'-bipy yields {[Zn(ACA)₂(4,4'-bipy)]·EtOH} _n (1), which was used for the formation of three CPs through dissolution-recrystallization structural transformations (DRSTs): {[Zn(ACA)₂(4,4'-bipy)]·2MeOH} _n (2), {[Zn₂(μ-ACA)₂(ACA)₂(4,4'-bipy)]·2H₂O} _n (3), and {[Zn₃(μ-ACA)₆(4,4'-bipy)]·0.75CHCl₃} _n (4). The study of the four crystal structures revealed that their secondary building units (SBUs) comprise monomeric, dimeric, and trimeric arrangements linked by 4,4'-bipy ligands. The fundamental role of the utilized solvent and/or temperature, as well as their effect on the orientation of the amide moieties driving the formation of the different SBUs is discussed. Furthermore, the reversibility and interconversion between the four CPs have been assayed. Finally, their solid-state photoluminescence has evinced that the effect of the amide moieties not only predetermine a different SBU but also lead to a different emission in 4 compared with 1-3.

Insight into charge transportation in cadmium based semiconducting organic-inorganic hybrid materials and their application in the fabrication of photosensitive Schottky devices

A coordination polymer (1) and a trinuclear complex (2) have been synthesized using a compartmental N₂O₂O₂' donor Schiff base ligand. Both complexes are characterized using different spectroscopic techniques and their structures are determined using single crystal X-ray diffraction analyses. Energies associated with different non-covalent (S⋯O chalcogen bonds, C-H⋯H-C, C-H⋯I and C-H⋯π) interactions in the solid state of both complexes have been calculated using the Turbomole program. Investigations of electrical conductivity and photosensitivity of both complexes reveal that suitable Schottky diode devices could be fabricated from both complexes. The current vs. voltage plots of the complex based devices have been used to calculate the conductivity under dark and irradiation conditions. In both complexes the charge transportation mainly occurs through space which involves the hopping process. Standard band theory has been used to compare the experimental and theoretical results of optoelectronic measurements. The calculations confirm that both are direct band gap (2.78 and 3.30 eV) semiconductors and that complex 1 exhibits a lower band gap, in line with the experimental results (3.21 and 3.43 eV in 1 and 2, respectively).

Enantioselective chiral sorption of 1-phenylethanol by homochiral 1D coordination polymers

Enantiomeric selectivity is shown within the pores of a 1D coordination polymer, dependent on the nature of the pore space.

Exploration of semiconducting properties of Zn(ii)- and Cd(ii)-based coordination polymers with dicarboxylate of a chair-type backbone

This study highlights the comparison of electrical properties and device applications of d10 metal ion based coordination polymers.