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Three new tertiary phosphane-appended heteroleptic Ni(II)-dithiolates with the formula [Ni(CAM)(dppe)] (Ni-1), [Ni(CAM)(dppf)] (Ni-2) and [Ni(CAM)(PPh3)2] (Ni-3) (CAM = cyanoacetamide dithiolate; dppe = 1,2-bis-(diphenylphosphinoethane); dppf = 1,1′-bis-(diphenylphosphino)ferrocene and PPh3 = triphenylphosphane) have been synthesized and characterized spectroscopically and using single crystal X-ray diffraction technique. The single crystal X-ray analysis of Ni-1, Ni-2 and Ni-3 reveal distorted square planar geometry around Ni(II), wherein Ni(II) is coordinated to the two sulfur centres of a CAM ligand in the bidentate chelating mode and two phosphorus centers of dppe, dppf and PPh3 ligands. Solid-state frameworks in these complexes are stabilized by C–O⋯H, C–N⋯H, C–S⋯H and C–H⋯C non-covalent intermolecular interactions. Ni-2 exhibits intramolecular (Ar)C–H⋯Ni anagostic interaction, which is absent in Ni-1 and Ni-3. Ni-3 exhibits intramolecular π⋯π stacking between the phenyl rings. The nature of these interactions have been assessed using Hirshfeld surface analyses, density functional theory (DFT) and quantum theory of atoms-in-molecules (QTAIM) calculations. Furthermore, the complexes have been employed as a homogeneous electrocatalyst for electrochemical hydrogen evolution reactions (HERs) using trifluoroacetic acid (TFA) as the hydrogen source. Electrochemical studies reveal turnover frequency (TOF) values of 319, 341 and 543 s−1 for Ni-1, Ni-2 and Ni-3, respectively, at 50 mM concentration of TFA. The plausible reason for the relatively better electrocatalytic activity of Ni-3 is ascribed to the coordination flexibility of the PPh3 ligand and the relatively larger positive natural charge over the nickel center and smaller HOMO–LUMO energy gap. [ABSTRACT FROM AUTHOR]

Metal–organic frameworks (MOFs) are a class of multimodal three-dimensional materials that have been applied as luminescent sensors for ions and molecules existing in water bodies. Herein, a new Cd(II)-based MOF, [H2bpd]2[Cd3(L)2] (1) (bpd = bis(pyridin-4-ylmethyl)propane-1,3-diamine; H5L = 3,5-di(2′,4′-dicarboxylphenyl)benzoic acid), was synthesized and characterized. Single crystal X-ray analysis revealed that 1 is anionic in nature and exhibits a flu-type topology with the point symbol (412·612·84)(46)2. This MOF was used as a turn-off photoluminescent sensor to detect Fe3+ and CrO42− by forming 1@Fe3+ and 1@CrO42− complexes, respectively. In the case of the Fe3+ cation, 1 displayed a KSV of 0.01763 and limit of detection (LOD) of 5.315 ppm, while for the chromate anion, it exhibited a KSV of 0.07338 and limit of detection of 1.277 ppm. Interestingly, the emissive response of 1 was restored upon the addition of hydroquinone (hyd) and 4-hydroxybenzoic acid (hyd acid) (turn-on) due to the competitive formation of hyd@Fe3+ or hyd acid@CrO42−, respectively, with the concomitant release of 1. The sensing properties of 1 and the recovery of its emission response in the presence of hyd and hyd acid were evaluated with the help of Hirshfeld surface and density functional theory analyses, respectively. The recovery of the emission property of 1 on the addition of hyd and hyd acid over other antioxidants arises because of their larger EHOMO and relatively less steric hindrance than those of the other oxidants employed in this study. [ABSTRACT FROM AUTHOR]

Four new heteroleptic Ni(II) complexes with the general formula [Ni(dppe)(L)] (dppe = 1,2-bis-(diphenylphosphino)ethane; L = 4-fluoro-benzyl cyanide dithiolate (Ni-1); 2-trifluoromethyl benzyl cyanide dithiolate (Ni-2); 3-trifluoromethyl benzyl cyanide dithiolate (Ni-3) and 4-trifluoromethyl benzyl cyanide dithiolate (Ni-4)) have been synthesized and characterized spectroscopically as well as by employing single crystal X-ray diffraction. Single crystal X-ray diffraction analyses for Ni-1 and Ni-3 reveal a distorted square planar geometry around the Ni(II) center satisfied by two sulfur and two phosphorus centers of dithiolate and dppe ligands, respectively. Both Ni-1 and Ni-3 form interesting supramolecular arrays sustained by C–H⋯F, C–S⋯H, C⋯H(Ar), C≡N⋯H and (Ar)C⋯F intermolecular interactions. These interactions have further been investigated using Hirshfeld surface analysis. These complexes have been used as heterogeneous electrocatalysts for oxygen evolution reaction (OER) studies and the results suggest that the electrocatalytic activity of Ni-1 outperforms the electrocatalytic activities of the other three complexes and it displays an η10 value of 814 mV and a Tafel slope of 94 mV dec−1. The study unveils the effects of fluoro- and trifluoromethyl substituents and the dihedral angle on the electrocatalytic properties towards the OER of these newly developed complexes. [ABSTRACT FROM AUTHOR]

Metal–organic frameworks (MOFs) constitute an assorted class of multi-dimensional materials that offer the potential to serve as luminescent sensors for the sensitive and selective detection of antibiotics in wastewater. Herein, a new Zn(II)-based MOF with the formula [Zn(PMA)0.5(bbp)·H2O·DMA] (1) (bbp = 3,5-bis(benzoimidazo-1-ly)pyridine; PMA = pyromellitic acid) was synthesized by a solvothermal method and characterized. Crystallographic analysis reveals that MOF 1 possesses a 4,4-connected net with the Schläfli symbol {32·4·52·6}2{32·42·52}. The fabricated MOF exhibited luminescent property and was employed as a luminescent sensor to sensitively and selectively detect tetracycline (TCY) antibiotic amongst thiamphenicol (THI), 2-methyl-4-chlorophenoxyacetic acid (MCPA), tetracycline (TCY), sulfamethoxazole (SMT), thiabendazole (TBZ), tinidazole (TDZ), sulfadiazine (SDZ), chloramphenicol (CAP), metamitron (MMT), and dinotefuran (DTF). Further, restoration of the emissive response of TCY@1 was achieved by adding salicylic acid with a concomitant bathochromic shift in the emissive response. The possible sensing mechanism and restoration of emissive response were assessed with the aid of theoretical calculations. [ABSTRACT FROM AUTHOR]

Two new heteroleptic cobalt(III)dialkyldithiophosphate complex cations with a 1,2-bis(diphenylphosphino)ethane (dppe) ancillary ligand having formula [Co{S2P(OR)2}2(dppe)](B(C6H5)4) (R = –C2H5 (Co–Et); –CH(CH3)2 (Co–Pr)) have been synthesized and characterized spectroscopically as well as via single crystal X-ray diffraction analysis. The single crystal X-ray diffraction analyses reveal that the immediate geometries around Co(III) in both complexes are distorted octahedral, which are satisfied by four sulfur atoms of two dialkyldithiophosphate ligands and two phosphorus centers of the dppe ligand. These complex cations are neutralized by tetraphenyl borate B(C6H5)4 anions. The solid-state framework of both complexes are stabilized by C–H⋯π and C–H⋯C interactions. The nature of these interactions have been addressed with the help of Hirshfeld surface analysis, and percent contributions of pertinent interactions in the crystal structure of these complexes have been addressed using fingerprint plots. Both complexes have been used as heterogeneous electrocatalysts for the oxygen evolution reaction (OER). Results suggest that Co–Et is a better electrocatalyst for the OER, displaying an onset potential of 1.68 V and Tafel slope of 114 mV dec−1. Furthermore, in the homogeneous electrocatalysis of the hydrogen evolution reaction (HER) using trifluoroacetic acid, the overpotential for Co–Et and Co–Pr have been 1.05 V and 0.92 V, respectively, with turnover frequencies of 1518 s−1 and 287.5 s−1, respectively. Overall, heterogeneous OER and homogenous HER results suggest that Co–Et can be used as an efficient molecular electrocatalyst for oxygen/hydrogen evolution reactions. [ABSTRACT FROM AUTHOR]

In this study, we synthesized and characterized a new Co(II)‐based coordination polymer, denoted as {[Co(HL)(dpa)]·H2O}n (1), derived from the H3L ligand and dpa co‐ligand. Single crystal X‐ray diffraction revealed that 1 forms a two‐dimensional (2D) layer and a three‐dimensional (3D) supramolecular structure via hydrogen bonding interactions. Presence of carboxylic acid groups in 1 was confirmed by X‐ray crystallography, prompting investigation into its proton transport properties. Additionally, electrostatic potential surface and nucleophilic index analyses were conducted to simulate potential proton transfer pathways. Furthermore, we prepared nine modified encapsulated materials using 1 as the base material (SDA@1, APH@1, APY@1, TA@1, BA@1, DIC@1, IDZ@1, SCA@1, and TYD@1), and tested their proton conductivity and activation energy compared to pure Nafion membrane and 1, analyzing the influence of different small molecule structures on proton conductivity. Comparative analysis revealed that only SDA@1 exhibited enhanced proton conductivity and reduced activation energy at 303 K, with an improvement rate of 220.8%. We hope that the methods presented herein can provide valuable insights for the design and development of high‐performance proton‐conducting materials, as well as for the exploration of proton conduction mechanisms. [ABSTRACT FROM AUTHOR]

New heteroleptic dppe appended Co(III)-dithiocarbamate (dtc) complex cations with compositions [Co(S2CNEt2)2(dppe)](PF6) (Co-Et), [Co(S2CNPri2)2(dppe)](PF6) (Co-Pr) and [Co(S2CNBun2)2(dppe)](PF6) (Co-Bu) have been synthesized and characterized by microanalysis, spectroscopic methods and crystallographic analysis. The single crystal X-ray diffraction results indicated that in all three complexes, the coordination environment around Co(III) is distorted octahedral and Co(III) is coordinated to four sulfur centers of the two dtc ligands and the two phosphorus centers of the dppe ligand. These complexes serve as precursors to yield cobalt sulfide/cobalt phosphide nano-composites dCo-Et, dCo-Pr and dCo-Bu by solvothermal decomposition of Co-Et, Co-Pr and Co-Bu, respectively. The decomposed materials have been characterized by PXRD and SEM-EDAX and explored as potential electrocatalysts for both oxygen evolution and hydrogen evolution reactions in basic and acidic media, respectively. Catalytic activity is dependent on the precursor complex and best OER and HER activities are observed for dCo-Bu with an η10 of 230 mV and a Tafel slope of 192.11 mV dec−1 for the OER and an η10 of 470 mV and a Tafel slope of 126.21 mV dec−1 for the HER. [ABSTRACT FROM AUTHOR]

Coordination polymers (CPs) with a d10-configuration containing metal cations offer interesting photoluminescent properties and hence can be employed as sensors to detect various classes of analytes. Moreover, due to their tuneable pore size they can be employed as adsorbents for various species. Herein, a new d10-configuration Cd(II)-based CP with composition {[Cd(bip)4(H2O)2]n·2NO3} (1) (bip = 3,5-bis(1-imidazol)pyridine) has been synthesized and characterized. Single-crystal X-ray analysis reveals that the Cd(II) center adopts octahedral geometry that is satisfied by four N atoms from the four bip linkers and two aqua ligands, and the resultant CP displays sql topology with the point symbol of (44·62). The CP offers prospective application as a photoluminescent sensor for dichromate anions with a limit of detection of 1.28 ppm and a Stern–Volmer constant (KSV) of 1.51 × 105. Furthermore, CP 1 was employed as an efficient adsorbent for dichromate ions, reaching an equilibrium adsorption capacity of 389.82 mg g−1 within 80 min. The effects of temperature, pH and concentration of dichromate were further investigated, which revealed that CP 1 displays the best adsorption at 30 °C and pH 4 with a dichromate concentration of 200 mg L−1. The possible adsorption mechanism has been proposed with the aid of Hirshfeld surface analysis. [ABSTRACT FROM AUTHOR]

Three new d8- and d10-configuration based 1,1′-bis-(diphenylphosphino)ferrocene (dppf) appended thiosquarates complexes with general composition [M(mtsq)2dppf] (M = Ni2+ (NiL2); Zn2+ (ZnL2) and Cd2+ (CdL2)) (mtsq = 3-ethoxycyclobutenedione-4-thiolate) have been synthesized and characterized spectroscopically as well as in case of NiL2 by single crystal X-ray diffraction technique. The single crystal X-ray analysis reveals square planar geometry around Ni(II) in NiL2, where Ni(II) coordinates with two sulfur centres of two mtsq ligands in monodentate fashion and two phosphorus of a dppf ligand in chelating mode. The supramolecular architecture of NiL2 is sustained by intermolecular C–H⋯O interactions to form one-dimensional chain. Further, the application of these newly synthesized complexes as sensitizers and co-sensitizers/co-absorbents with ruthenium based N719 sensitizer in dye-sensitized solar cells (DSSCs) have been explored. The DSSC set-up based on NiL2 offers best photovoltaic performance with photovoltaic efficiency (η) 5.12%, short-circuit current (Jsc) 11.60 mA cm−2, open circuit potential (Voc) 0.690 V and incident photon to current conversion efficiency (IPCE) 63%. In co-sensitized DSSC set-up, ZnL2 along with state-of-the-art N719 dye displays best photovoltaic performance with η 6.65%, Jsc 14.47 mA cm−2, Voc 0.729 V and IPCE 69%, thereby showing an improvement by 15.25% in photovoltaic efficiency in comparison to the photovoltaic efficiency of N719 sensitized DSSC set-up. Variation in co-sensitization behaviour have been ascribed to the differences in the excited state energy level of co-sensitizers. The ZnL2 and CdL2 have a higher energy level position than N719 dye, allowing efficient electron transfer to N719 during light irradiation, while excited state of NiL2 is lower than N719 dye, preventing photoexcited electron transfer to N719, resulting in its lowest overall efficiency among the three co-sensitized DSSC setups. [ABSTRACT FROM AUTHOR]

Coordination polymers are a sub-class of coordination complexes that possess unique opto-electronic properties and hence can be utilized for a wide range of applications such as sensing and photocatalysis. Herein, four new coordination polymers (CPs) with formula [Mn2(HL)(NMP)(H2O)2]n (1), [Mn2(HL)(DMA)2(H2O)·2DMA]n (2), [Mn(H3L)(H2O)2]n (3) and [Mn(H3L)(H2O)(4,4′-bipy)]n (4) (H5L = 3,5-bis(3,4-dicarboxyphenoxy) benzoic acid and NMP = N-methyl pyrrolidone) were synthesized under hydrothermal conditions and characterized. The single-crystal X-ray analysis revealed a distorted octahedral geometry around Mn(II) in these CPs and that they form an extended hydrogen bonding and π⋯π stacking interaction-assisted network. Thermogravimetric studies revealed that the CPs, 1, 2, 3 and 4, have variable thermal stability in the range of 82–194 °C. All four complexes exhibited optical semiconducting behavior and hence were used as photocatalysts for the photodecomposition of antibiotics, including chloramphenicol (CAP), nitrofurazone (NFZ), ornidazole (ODZ), oxytetracycline (OXY) and sulfamethoxazole (SMT). Among the CPs, CP 2 exhibited an impressive 91.93% degradation of NFZ within 60 min. The plausible photocatalytic mechanism was explained with the assistance of Hirshfeld surface analysis. [ABSTRACT FROM AUTHOR]

A new heteroleptic Ni(II) dithiolate [Nidppe(dtsq)] (Nidtsq) (dppe = 1,2-bis-(diphenylphosphino)ethane, dtsq2− = 3,4-dioxocyclobut-1-ene-1,2-dithiolate) has been synthesised and characterized spectroscopically and by single crystal X-ray diffraction. The single crystal X-ray diffraction study reveals a square planar geometry around the Ni(II) center wherein dtsq2− and dppe ligands exhibit bidentate chelating coordination modes by their respective sulfur and phosphorus centers. The solid-state framework of Nidtsq is stabilized by C–H⋯O, C⋯H, C⋯O and π⋯π intermolecular interactions and the complex displays an interesting pair of intramolecular C–H⋯Ni anagostic interactions. The nature of these interactions has been addressed with Hirshfeld surface analysis, density functional theory, quantum theory of atoms and molecules (QTAIM) and non-covalent interaction-reduced density gradient (NCI-RDG) analyses. Furthermore, the electrocatalytic properties of Nidtsq have been assessed for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). The electrocatalytic properties of Nidtsq have been found to be better than those of the previously reported Ni-mtsq complex.17 In the OER, the complex displayed an overpotential of 0.37 V with η10 of 414 mV and a Tafel slope of 237 mV dec−1 and in the HER it exhibited an overpotential of −0.35 V with η10 of −670 mV and a Tafel slope of 368 mV dec−1. Chronoamperometry and chronopotentiometry experiments for four hours in 0.1 M KOH and 0.5 M H2SO4 indicate the robustness of the complex in alkaline and acidic environments and the post-electrocatalytic stability of Nidtsq has been assessed with the aid of FESEM and X-ray photoelectron spectroscopy. [ABSTRACT FROM AUTHOR]

In this study, two new heteroleptic complexes with compositions [Ni(mtsq)1.85Cl0.15(dppe)](CH2Cl2)0.06(CH3OH)0.09 (Ni-mtsq) and [Cu(mtsq)(PPh3)2] (Cu-mtsq) (dppe = 1,2-bis-(diphenylphosphino)ethane; PPh3 = triphenylphosphane and mtsq = 3-ethoxycyclobutenedione-4-thiolate) have been synthesized and characterized by spectroscopy analyses as well as by single crystal X-ray diffraction technique. X-ray analyses reveal square planar geometry around Ni(II) in Ni-mtsq, where Ni(II) coordinates with two sulfur centres of two mtsq ligands with monodentate coordination and two phosphorus centres of the dppe ligand in chelating mode. Unlike Ni-mtsq, Cu(I) in Cu-mtsq adopts a tetrahedral geometry, which is satisfied by sulfur and oxygen centres of one mtsq ligand with a bidentate coordination mode and two phosphorus centres of two PPh3 ligands. The supramolecular architecture of both Ni-mtsq and Cu-mtsq is sustained by intermolecular C–H⋯π and O⋯H interactions. Also, Ni-mtsq exhibits intriguing intramolecular semicoordination Ni⋯O and π⋯π non-covalent interactions. The nature of these interactions has been addressed with the aid of Hirshfeld surface analysis, density functional theory and quantum theory of atoms in molecules (QTAIM) analyses and has been visualized with the help of non-covalent interactions reduced density gradient (NCI-RDG). Further, the emissive nature of Cu-mtsq in a solution and solid phase suggests aggregation-induced emission with a bathochromic shift in the solid phase as compared to the solution phase. Both complexes have been used as electrocatalysts for oxygen and hydrogen evolution reactions, which suggests that Cu-mtsq offers better catalysis due to the presence of a redox active, less hindered Cu(I) centre with an η10 of 600 mV and a Tafel slope of 228 mV dec−1 in the OER, while in HER too, Cu-mtsq exhibited the best onset potential of −0.36 V with an η10 of 647 mV. Also, homogeneous electrocatalysis for the HER for both complexes was investigated using trifluoroacetic acid as the hydrogen source, which suggests a better electrocatalytic performance of Cu-mtsq. [ABSTRACT FROM AUTHOR]

Three new isomeric 1,1′-bis-(diphenylphosphino)ferrocene (dppf) appended nickel(II) dithiolates o-NiL , m-NiL and p-NiL (disodium 2-cyano-2-(2-methoxyphenyl)ethene-1,1-dithiolate (o-L), disodium 2-cyano-2-(3-methoxyphenyl)ethene-1,1-dithiolate (m-L) and disodium 2-cyano-2-(4-methoxyphenyl)ethene-1,1-dithiolate (p-L)) have been synthesized and characterized. The single X-ray analyses revealed that in all three complexes, nickel(II) adopts a distorted square planar geometry arising from the bidentate chelating coordination of two sulfur centers of the dithiolate ligand and two phosphorus centers of the dppf co-ligand. The distortion in geometry is because of the strained four membered NiS2C chelate ring formed from the dithiolate ligand as well as small variation in Ni–S and Ni–P bond lengths. The weak interactions existing in these newly synthesized sensitizers have been addressed with the help of Hirshfeld surface analysis. The electronic absorption spectra of all three compounds display absorption bands between ∼400–500 nm and ∼500–600 nm arising from the d–d transition of ferrocene and Ni(II), respectively. These compounds have been used as photo-sensitizers in dye sensitized solar cells (DSSCs). The experiments revealed that amongst all three sensitizer based DSSC set-ups, the assembly fabricated using p-NiL exhibited the best photovoltaic performance due to stronger electronic coupling between the sensitizer and the semiconductor resulting in enhanced electron injection with 3.40% efficiency (η) with a short circuit current (Jsc) of 7.10 mA cm−2, open circuit voltage (Voc) of −0.748 V and incident photon to current conversion efficiency of 63%. Also, the ageing experiment for the DSSC cell set-up fabricated using p-NiL revealed that after 700 h the set-up retained 93% of its efficiency which indicates that such a type of molecular system can be used as an apt sensitizer for DSSC fabrication. [ABSTRACT FROM AUTHOR]

Three new d 8 - and d 10 -configuration based 1,1'-bis-(diphenylphosphino)ferrocene (dppf) appended thiosquarates complexes with general composition [M(mtsq) 2 dppf] (M = Ni 2+ (NiL2); Zn 2+ (ZnL2) and Cd 2+ (CdL2)) (mtsq = 3-ethoxycyclobutenedione-4-thiolate) have been synthesized and characterized spectroscopically as well as in case of NiL2 by single crystal X-ray diffraction technique. The single crystal X-ray analysis reveals square planar geometry around Ni(II) in NiL2, where Ni(II) coordinates with two sulfur centres of two mtsq ligands in monodentate fashion and two phosphorus of a dppf ligand in chelating mode. The supramolecular architecture of NiL2 is sustained by intermolecular C-H⋯O interactions to form one-dimensional chain. Further, the application of these newly synthesized complexes as sensitizers and co-sensitizers/co-absorbents with ruthenium based N719 sensitizer in dye-sensitized solar cells (DSSCs) have been explored. The DSSC set-up based on NiL2 offers best photovoltaic performance with photovoltaic efficiency ( η ) 5.12%, short-circuit current ( J sc ) 11.60 mA cm -2 , open circuit potential ( V oc ) 0.690 V and incident photon to current conversion efficiency (IPCE) 63%. In co-sensitized DSSC set-up, ZnL2 along with state-of-the-art N719 dye displays best photovoltaic performance with η 6.65%, J sc 14.47 mA cm -2 , V oc 0.729 V and IPCE 69%, thereby showing an improvement by 15.25% in photovoltaic efficiency in comparison to the photovoltaic efficiency of N719 sensitized DSSC set-up. Variation in co-sensitization behaviour have been ascribed to the differences in the excited state energy level of co-sensitizers. The ZnL2 and CdL2 have a higher energy level position than N719 dye, allowing efficient electron transfer to N719 during light irradiation, while excited state of NiL2 is lower than N719 dye, preventing photoexcited electron transfer to N719, resulting in its lowest overall efficiency among the three co-sensitized DSSC setups.