Terpyridine Moieties Research Articles

Stoichiometrically Controlled Assembly of Lanthanide Molecular Complexes of the Heteroditopic Divergent Ligand 4'-(4-Pyridyl)-2,2':6',2″-terpyridine N-Oxide in Hypodentate or Bridging Coordination Modes. Structural, Magnetic, and Photoluminescence Studies.

Mononuclear rare-earth tris-β-diketonato complexes RE(tta)3dme [RE = Y (1), La (2), Dy (3), or Eu (4); Htta = 2-thenoylacetone; dme = 1,2-dimethoxyethane] react cleanly at room temperature in a 1:1 molar ratio with the heteroditopic divergent ligand 4'-(4-pyridyl)-2,2':6',2″-terpyridine N-oxide (pyterpyNO) to yield RE2(tta)6(pyterpyNO)n, where n = 2 for RE = Y (5), Dy (6), or Eu (7) and n = 3 for RE = La (8). The crystal structure of 5 revealed a dinuclear compound with two pyterpyNO's bridging through the oxygen atom in a hypodentate mode leaving the terpyridine moieties uncoordinated. Using a metal:pyterpyNO molar ratio of 2 for RE = Y (9), Dy (10), or Eu (11), it was possible to isolate the molecular complexes RE4(tta)12(pyterpyNO)2, while using a 5:3 molar ratio, the product La5(tta)12(pyterpyNO)3 (12) can be obtained. 89Y nuclear magnetic resonance spectroscopy revealed two different yttrium centers at room temperature for 9. An X-ray diffraction study of 10 showed a symmetrical tetranuclear structure resulting from the coordination of two Dy(tta)3 fragments to the two hypodentate terpyridines of the dinuclear unit and presenting two different coordination sites for metals with coordination numbers of 8 and 9. Magnetic studies of 6 and 10 revealed the presence of an antiferromagnetic interaction between the two Dy(III) atoms bound by the NO bridges. These compounds displayed a slow relaxing magnetization through Orbach (6) and Raman (10) processes in the absence of an applied magnetic field; the rate increased upon application of a 1 kOe field. 7 and 11 showed a bright red emission typical of Eu3+. The two complexes have similar emission properties mainly determined by the employed β-diketonato ligands.

Just Add the Gold: Aggregation-Induced-Emission Properties of Alkynylphosphinegold(I) Complexes Functionalized with Phenylene-Terpyridine Subunits.

A series of organometallic complexes containing an alkynylphosphinegold(I) fragment and a phenylene-terpyridine moiety connected together by flexible linker have been prepared using the specially designed terpyridine ligands. The compounds were studied crystallographically to reveal that all of them contain a linearly coordinated Au(I) atom and a free terpyridine moiety. The different orientations of the molecules relative to each other in the solid state determine the multiple noncovalent interactions such as antiparallel ππ stacking, CH-π, and CH-Au, but no aurophilic interactions are realized. The organometallic Au(I) complexes obtained show fluorescence in the solution and dual singlet-triplet emission in the solid state. This means that their photophysical behavior is determined by both intermolecular lattice-defined interactions and Au(I) atom introduction. Density functional theory computational analysis supported the assignment of emission to intraligand electronic transitions only inside the phenylene-terpyridine part with no Au(I) involved. In addition, a study of the nature of the excited states for the "dimer" with an antiparallel orientation of the terpyridine fragment showed that this orientation leads to the generation of abstracted singlet and triplet states, lowering their energy in comparison with the monomer complex. Thus, the complexes obtained can be qualified as examples of Au(I)-containing organometallic aggregation-induced-emission luminogens.

BODIPY-Ruthenium(II) Bis-Terpyridine Complexes for Cellular Imaging and Type-I/-II Photodynamic Therapy.

A series of multichromophoric ruthenium(II) complexes with the formulation [Ru(tpy-BODIPY)(tpy-R)]Cl2 (1-4), having a heteroleptic Ru(II)-bis-tpy (tpy = 4'-phenyl-2,2':6',2″-terpyridine) moiety covalently linked to a boron-dipyrromethene (BODIPY) pendant, have been prepared and characterized and their application as a phototherapeutic and photodetection agent in cancer therapy has been explored. Ligand L1 with a terpyridine-BODIPY moiety and complex 1 as its PF6 salt (1a) have been structurally characterized by a single-crystal X-ray diffraction study. Complex 1a has a distorted-octahedral RuN6 core with a Ru(II)-bis-terpyridine unit that is covalently linked to one photoactive BODIPY unit. The complexes exhibit strong absorbance near 502 nm (ε ≈ (3.7-7.8) × 104 M-1 cm-1) and high singlet oxygen sensitization ability, giving singlet oxygen quantum yield (ΦΔ) values ranging from 0.57 to 0.75 in DMSO. An emission-based study using complex 4 and Singlet Oxygen Sensor Green (SOSG) displays the formation of singlet oxygen inside the cells and also in the buffer medium upon light irradiation. DNA (pUC19) photocleavage experiments using ROS scavengers/stabilizers reveal photoinduced generation of singlet oxygen by a type-II process and of the superoxide anion radical by a type-I process. Complex 4 having a pendant biotin moiety as a cancer cell targeting group shows high photocytotoxicity with a remarkable phototherapeutic index (PI) value of >1400 in HeLa cancer cells with a low light dose activation (400-700 nm, 2.2 J cm-2). The complexes display reduced activity in noncancerous HPL1D cells. The emission property of the complexes is used for cellular imaging, thus making them suitable as next-generation theranostic PDT agents.

Designing narcissistic self-sorting terpyridine moieties with high coordination selectivity for complex metallo-supramolecules

Coordination-driven self-assembly is a powerful approach for the construction of metallosupramolecules, but designing coordination moieties that can drive the self-assembly with high selectivity and specificity remains a challenge. Here we report two ortho-modified terpyridine ligands that form head-to-tail coordination complexes with Zn(II). Both complexes show narcissistic self-sorting behaviour. In addition, starting from these ligands, we obtain two sterically congested multitopic ligands and use them to construct more complex metallo-supramolecules hexagons. Because of the non-coaxial structural restrictions in the rotation of terpyridine moieties, these hexagonal macrocycles can hierarchically self-assemble into giant cyclic nanostructures via edge-to-edge stacking, rather than face-to-face stacking. Our design of dissymmetrical coordination moieties from congested coordination pairs show remarkable self-assembly selectivity and specificity.

Light and Cation-Driven Optical Switch based on a Stilbene-Appended Terpyridine System for the Design of Molecular-Scale Logic Devices

A molecular system comprising a terpyridine moiety capable of coordinating with different cations and a photoswitchable stilbene unit has been utilized here for the fabrication of multiply configurable logic systems. Incorporation of a substituted stilbene unit into the terpyridine motif generates an intraligand charge-transfer-sensitive module whose absorption and emission spectral properties are highly sensitive to light as well as cations. On the basis of the optical response profile of the receptor in the presence of selected cations as well as light of a specific wavelength, we are able to demonstrate multiple Boolean logic functions such as INHIBIT, IMPLICATION, OR, NOR, and NAND, as well as various combinations of them. Of particular interest, we utilized the present system for the construction of security keypad locks and memory devices by maintaining a proper sequence of the stimuli and monitoring either absorption or emission spectral response at a specific wavelength as the output signal. In addition to various Boolean logic functions, the present system has also the ability to mimic fuzzy logic operations for generating an infinite-valued logic scheme depending on its emission spectral responses upon varying the concentration of cationic (Fe2+ and/or Zn2+) and anionic (CN-) inputs.

Reversible Hydrogels with Switchable Diffusive Permeability

AbstractHydrogels are polymer networks swollen in water that are characterized by soft mechanics and high permeability. This makes them good candidates for separation and membrane technologies. The diffusion is controlled by the mesh size of the network, and this can be made tunable through the introduction of thermoresponsive polymers. However, this is still a developing field. To contribute to this development, a dual dynamic network is formed composed of four‐arm polyethylene glycol precursors in which each arm is functionalized with both a terpyridine moiety capable of forming reversible metal–ligand complexes along with branches of poly(N‐isopropylacrylamide) (pNIPAAm), which can be switched between expanded and collapsed states and therewith offers a path for switching the microscopic gel‐network mesh size, along with the macroscopic gel elasticity. The dually sensitive hydrogel has the capability of doubling its elastic modulus when going above the lower critical solution temperature (LCST) of pNIPAAm. In addition, the diffusive permeability of the hydrogel is switched upon change of temperature, whereby diffusants are trapped above the LCST of pNIPAAm. Moreover, it is possible to disassemble and reform the gel upon change of pH. With that, the hydrogel has potential application as a switchable and reversible membrane.

Spin Crossover and Field‐Induced Single‐Molecule Magnet Behaviour in Co(II) Complexes Based on Terpyridine with Tetrathiafulvalene Analogues

AbstractTwo new TTF‐based ligands involving terpyridine moiety (L1=4‐(4′‐Methyl‐phenyl‐2,2 : 6’,2’’‐terpyridine −4‐ylmethylthio)‐5‐(2‐cyanoethylthio)‐4′,5′‐bis(methylthio)tetrathiafulvene and L2=4‐(4′‐Methyl‐phenyl‐2,2 : 6’,2’’‐terpyridine −4‐ylmethylthio)‐5‐(2‐cyanoethylthio)‐4′,5′‐bis(propylthio)tetrathiafulvene) have been synthesized and seven related mononuclear complexes were isolated as single crystals. The 2 : 1 (ligand : metal) complexes of formula [Co(L1)2](NO3)2 (2) and [Co(L1)2](BF4)2 (3) displayed thermal spin crossover transition while the 1 : 1 complexes of formula [CoCl2(L1)](DMF)2 (4), [CoBr2(L1)] ⋅ (DMF) (5), [CoCl2(L2)] ⋅ (DMF) ⋅ 0.5(Et2O) (6) and [CoBr2(L2)] ⋅ (DMF) (7) displayed slow magnetic relaxation through either Raman or Raman/Direct combination processes. A relationship between the structure and the nature of the magnetic relaxation processes is proposed.

(Invited) Helicate Europium Complexes for the Design of Efficient Luminescence and Electro-Luminescence Devices

Molecular structure in metal complexes enhances their electronic structure and physicochemical properties such as luminescence. It is well known that the number of coordination of a lanthanide ion is various from six to twelve. Here, we will introduce a series of helicate europium (Eu) complexes which having hexadentate ligand with chelate effect to keep the coordination of its aromatic ligand as photo-antenna to induce ff emissions of Eu.[1] The Eu complex (EuL) has a neutral ligand consisted in two bipyridine moieties bridged by ethylenediamine and two nitrate ions, and takes a cationic complex. The molecular structure succeeded to form the efficient energy donor behavior from the measurement of electro-static potential by the synchrotron single crystal X-ray analysis (SPring-8, BL01B1), because the bipyridine moiety has kept the excited state like a terpyridine moiety. The luminescence band of Eu was observed at 616 nm with relatively high luminescent quantum yields (QY) by UV excitation. The complex is also soluble in ionic liquids (IL) when the same counter anions were used in both the complex and IL such as PF6 -.[2] Luminescence and electronic absorption bands position of EuL in IL were same. Interestingly the QY of the complex drastically increased in IL because of the high viscosity. IL was also useful for the application for electrochemistry as a medium. Actually, there are several papers of Eu complexes were reported to explain the possibility of luminescence color change by the redox reaction of Eu ion[3]. If Eu ion takes divalent state, the luminescence color will be shifted at blue, and can be switch the color between red and blue by electrochemistry. In the case of EuL in IL, we adopted the solution to electronic cells and found the luminescence intensity changing at around +2.0 and -1.8 V [4]. It exhibites the reversibility with keeping the possible luminescence intensity. Thus, the stable halicate structure and cationic state of EuL act as a electrochemical active behavior in IL.Author acknowledges Professor Y. Kim, Hokkaido University for the collaboration of electrochemistry in the ionic liquids.[1] (a)M. Hasegawa, et al., New J. Chem., 2014, 38, 1225-1234; (b) M. Hasegawa, et al., ChemPlusChem, 2020, 85, 294-300; (c) M. Hasegawa, et al., Photochem. Photobiol. Sci., 2020, DOI: 10.1039/d0pp00069h, (d) M. Hasegawa & H. Ohmagari, Chem. Lett., 2020, 49, 845-854.[2] Y. Hasegawa, M. Hasegawa, et al., Molecules, 2018, 23, 55.[3] (a)K. Binnemans, Chem Rev, 2007, 107(6), 2592–2614; (b) M. Mukaigawa & H. Ohno, Solid State Ionics, 1998, 113-115, 439-442.[4] Y. Kim & M. Hasegawa, et al., 2020, DOI:10.1021/acsami.0c13765. Figure 1

Double-Decker Silsesquioxanes Self-Assembled in One-Dimensional Coordination Polymeric Nanofibers with Emission Properties.

The urgent needs for photoactive materials in industry drive fast evolution of synthetic procedures in many branches of chemistry, including the chemistry of silsesquioxanes. Here, we disclose an effective protocol for the synthesis of novel double-decker silsesquioxanes decorated with two (styrylethynylphenyl)terpyridine moieties (DDSQ_Ta-b). The synthesis strategy involves a series of silylative and Sonogashira coupling reactions and is reported for the first time. DDSQ_Ta-b were employed as nanocage ligands to promote self-assembly in the presence of transition metals (TM), i.e., Zn2+, Fe2+, and Eu3+ ions, to form one-dimensional (1D) coordination polymeric nanofibers. Additionally, ultraviolet-promoted and reversible E–Z isomerization of the C=C bond within the ligand structures may be exploited to tune their emission properties. These findings render such complexes promising candidates for applications in materials chemistry. This is the first example of 1D coordination polymers bearing DDSQ-based nodes with TM ions.

Exploitation of the Second Coordination Sphere to Promote Significant Increase of Room-Temperature Luminescence Lifetime and Anion Sensing in Ruthenium–Terpyridine Complexes

This paper deals with the synthesis, characterization, and photophysical behaviors of three Ru(II)-terpyridine complexes derived from a terpyridyl-imidazole ligand (tpy-HImzPh3Me2), wherein a terpyridine moiety has been coupled with a dimethylbenzil unit through a phenylimidazole spacer. The three complexes display strong emission at RT having excited-state lifetimes in the range of 2.3-43.7 ns, depending upon the co-ligand present and the solvents used. Temperature-dependent emission spectral measurements have demonstrated that the energy separation between emitting metal-to-ligand charge transfer state and non-emitting metal-centered state is increased relative to that of [Ru(tpy)2]2+. In contrast to our previously studied Ru(II) complexes containing similar terpyridyl-imidazole motif but differing by peripheral methyl groups, significant enhancement of RT emission intensity and quantum yield and remarkable increase of emission lifetime occur for the present complexes upon protonation of the imidazole nitrogen(s) with perchloric acid. Additionally, by exploiting imidazole NH motif(s), we have examined their anion recognition behaviors in organic and aqueous media. Interestingly, the complexes are capable of visually recognizing cyanide ions in aqueous medium up to the concentration limit of 10-8 M. Computational studies involving density functional theory (DFT) and time-dependent DFT methods have been carried out to obtain insights into their electronic structures and to help with the assignment of absorption and emission bands.

Highly sensitive fluorescent sensor based on coumarin organic dye for pyrophosphate ion turn-on biosensing in synovial fluid

Highly sensitive fluorescence detection of pyrophosphate ion (PPi) is in urgent demand but remains a great obstacle, ascribing to scarcity of high-performance materials with promising optical property and high affinity. Herein, we report the design and fabrication of a coumarin-based organic dye (DCCH-TPD) containing both hydrazide group and terpyridine moiety for PPi biosensing through Cu2+-induced photo-electron transfer (PET) effect and target analyte-switched competitive coordination reaction. Individual DCCH-TPD was found to be highly emissive, and displayed a turn-off response toward Cu2+ due to formation of Cu2+@DCCH-TPD and PET effect. The recognition of Cu2+@DCCH-TPD by PPi leads to generation of Cu2+@PPi complex, which greatly reduces the amount of Cu2+ coordinated with DCCH-TPD, subsequently decreasing PET effect. Significantly enhanced fluorescence is recorded and the fluorescence intensity is closely relied on PPi concentration. Thus, highly sensitive detection of PPi is achieved, and the detection limit was calculated to be 0.075 μM. Furthermore, the proposed sensor presented good selectivity, and excellent practical ability for application in arthritic fluid.

Molecular engineering of head-tail terpyridine-Fe(II) coordination polymers employing alkyl chain linkers toward enhanced electrochromic performance

For the first time, we demonstrated that employing long alkyl chains as a nonconjugated linker in ditopic ligands is a promising strategy to construct Fe(II) coordination polymers for efficient electrochromics. Three new Fe(II) coordination polymers with ditopic organic ligands, in which two terpyridine moieties were connected by nonconjugated alkylchain linkers were synthesized. The morphology and hydrophobicity of the thin film made from the Fe(II) coordination polymers can be adjusted by changing the length of alkylchain linker. Benefiting from the longer length of the linker, the ditopic terpyridine-Fe coordination polymer FeL2 performed superior electrochromic performance as compared to FeL1 in the same condition, including shorter switch time, lower operation potential, higher optical contrast and coloration efficiency. Remarkably, the elaborate coordination polymer FeL2 exhibited the highest optical contrast up to 76% among the reported electrochromic materials based on Fe-complexes up to date. Due to the hydrophobic property of FeL3 probably benefit from its longer alkyl chain linkers, we carried out the electrochromic switch based on ionic Fe(II) coordination polymers using aqueous electrolyte for the first time.

Synthesis, characterization and molecular docking study of Nitro(4′-(2-pyridyl)-2,2′:6′,2″-terpyridyl) Palladium(II) nitrate

The title compound Nitro(4′-(2-pyridyl)-2,2′:6′,2″-terpyridyl) palladium(II) nitrate, 1 consists of a terpyridyl derivative 4′-(2-pyridyl)-2,2′:6′,2″-terpyridyl, (terpy) L bonded to a Pd(II) unit through Pd-N coordinate bond. The complex 1 is characterized by 1H, 13C NMR, H-H COSY, C-H COSY and by single crystal X-ray diffraction technique. The NMR data of complex shows the diamagnetic shielding of the signal due to terpy α-proton. The crystal structure of the compound shows that the fourth coordination site of palladium is occupied by a nitrate ion. The electrical neutrality of the complex is maintained by another nitrate ion present outside of the coordination sphere. The core structure of the terpyridine moiety lies almost co-planar and the substituted pyridine group is slightly twisted with respect to the core structure. The dihedral angle between the substituted pyridine group and the mean plane passing through the core terpyridine unit is found to be approximately 12°. Further analysis of the crystal structure show one molecule of the complex cation 1 is linked to two other molecules (one on either side) by inter molecular π-π stacking interaction and forms a one dimensional π-polymer. Several of these π-polymers engaged in further π-π stacking to form the three dimensional array. The complex 1 shows the ability to bind to B-DNA. Molecular docking studies show that complex 1 binds to the minor grove of B-DNA with an attractive van der Waals energy of −7.48 kcal/mol.

Hydrogen bond-induced abrupt spin crossover behaviour in 1-D cobalt(II) complexes - the key role of solvate water molecules.

The magnetic properties and structural aspects of the 1-D cobalt(ii) complexes, [Co(pyterpy)Cl2]·2H2O (1·2H2O; pyterpy = 4'-(4'''-pyridyl)-2,2':6',2''-terpyridine) and [Co(pyethyterpy)Cl2]·2H2O (2·2H2O; pyethyterpy = 4'-((4'''-pyridyl)ethynyl)-2,2':6',2''-terpyridine) are reported. In each complex the central cobalt(ii) ion displays an octahedral coordination environment composed of three nitrogen donors from the terpyridine moiety, a nitrogen donor from a pyridyl group and two chloride ligands which occupy the axial sites. 1·2H2O exhibits abrupt spin-crossover (SCO) behaviour (T1/2↓ = 218 K; T1/2↑ = 227 K) along with a thermal hysteresis loop, while 2·2H2O and the dehydrated species 1 and 2 exhibit high-spin (HS) states at 2-300 K as well as field-induced single-molecule magnet (SMM) behaviour attributed to the presence of magnetic anisotropic HS cobalt(ii) species (S = 3/2). 1·2H2O exhibited reversible desorption/resorption of its two water molecules, revealing reversible switching between SCO and SMM behaviour triggered by the dehydration/rehydration processes. Single crystal X-ray structural analyses revealed that 1·2H2O crystalizes in the orthorhombic space group Pcca while 2 and 2·2H2O crystallize in the monoclinic space group P2/n. Each of the 1-D chains formed by 1·2H2O in the solid state are bridged by hydrogen bonds between water molecules and chloride groups to form a 2-D layered structure. The water molecules bridging 1-D chains in 1·2H2O interact with the chloride ligands occupying the axial positions, complementing the effect of Jahn-Teller distortion and contributing to the abrupt SCO behaviour and associated stabilization of the LS state.

Novel Ru(II)/Os(II)‐Exchange Homo‐ and Heterometallic Polypyridyl Complexes with Effective Energy Transfer

AbstractTwo novel homometallic Ru−Ru and heterometallic Ru−Os dimers and trimers, [MII(bpy)2(4‐tpy‐4′‐methyl‐2,2′‐bipyridine)MII(tpy)]4+ and [MII(bpy)2](4‐tpy‐4′‐tpy‐2,2′‐bipyridine)(MII(tpy))2]6+, have been first prepared and characterized. Electrochemical properties of the metal‐based reversible oxidation and ligand‐based reduction are measured. Spectroscopic analysis of these complexes exhibits for every Ru‐ or Os‐based subunit an individual intense absorption spectrum extended over the entire UV and visible region. The heteronuclear complexes [RuII(bpy)2(4‐tpy‐4′‐methyl‐2,2′‐bipyridine)OsII(tpy)]4+, [RuII(bpy)2](4‐tpy‐4′‐tpy‐2,2′‐bipyridine)(OsII(tpy))2]6+, and [OsII(bpy)2](4‐tpy‐4′‐tpy‐2,2′‐bipyridine)(RuII(tpy))2]6+ display a weak emission spectrum in the near‐infrared region (NIR). The luminescence of the polynuclear assemblies is quantitatively quenched, by intramolecular energy transfer to the lower‐lying metal‐to‐ligand charge transfer (3MLCT) and metal‐centered (3MC) state of the Os(II)‐based center or Ru(II)‐terpyridine moiety at room temperature.

Synthesis of an Alternated Heterobimetallic Supramolecular Polymer Based on Ru(II) and Fe(II).

A heterobimetallic supramolecular polymer (polyRuFe) with alternately complexed Ru(II) and Fe(II) is prepared following a stepwise synthetic route through harnessing first the strongly binding metal ion Ru(II) and then the weakly binding metal ion Fe(II). A high yield of product is achieved in each step. The heterometal ions are incorporated into the polymer chain in identical coordination environments formed by two 2,2′:6′,2″-terpyridine moieties. Characterization is accomplished by NMR spectroscopy, MALDI–TOF mass spectrometry, UV–Vis spectroscopy, and cyclic voltammetry. PolyRuFe shows a wide optical window (λ = 311–577 nm) and a broad distinct reversible redox nature of two types, originated from the coupling of the two heterometallic segments into the polymer chain. Such characteristics of polyRuFe suggest its potential for various electrochemical and electro-optical applications.

Supramolecular and Physically Double-Cross-Linked Network Strategy toward Strong and Tough Elastic Fibers.

The strength and toughness are two trade-off properties of a material, yet Nature can achieve strong and tough materials by introducing sacrificial bonds into a system. Here, we present a four-component multiblock copolymer (mBCP) approach toward strong and tough elastic fibers, by introducing terpyridine moieties into poly(ether ester) mBCP elastomers. After coordination with Fe(II), supramolecular cross-links are formed within the physically cross-linked thermoplastic elastomers. The toughening elastic fibers with a double-cross-linked network structure show high tensile strength (ca. 300 MPa) and toughness (ca. 100 MJ m-3). In addition, they display excellent resilience with enhanced self-healing properties. Our strategy provides a promising way for the development of strong and tough elastomers by introducing metal-ligand sacrificial bonds into mBCPs elastomers.

Terpyridine-Containing Porphyrin and Coordination Assembly with Fullerene-Based Pyridine for Enhanced Electrocatalytic Oxygen Evolution and Photocurrent Response

Terpyridine-modified porphyrin, ZnP-Pr-tpy, had been synthesized and fully characterized by MS, NMR, IR and UV-Vis. The electrocatalytic activity of ZnP-Pr-tpy is improved with respect to that of the porphyrin un-modified with terpyridine (ZnP-Pr-Br), and further enhanced by forming a composite film with the fullerene-based pyridine(C60-py),these can be ascribed to the improvement in the intra- and intermolecular electron transfer and the decrease in the electrochemical impedance as result of the axial coordination of C60-py to ZnP-Pr-tpy and the π-π interaction. The photoelectrochemical test results show that the covalently modification of porphyrin with terpyridine moiety lead to a improvement in the photocurrent response,which can be attributed to the electron-exchang in ZnP-Pr-tpy through the Dexter energy transfer mechanism under light excitation, and the ground state electrons transferred from the terpyridine moiety to the porphyrin unit, and the photocurrent response is further enhanced after forming a ZnP-Pr-tpy/C60-py composite film, which due to the light-induced electron transfer via coordination bond in the ZnP-Pr-tpy/C60-py assembly.

Kinetics and mechanistic study of electrocatalytic hydrogen evolution by [Co(Fc-tpy)2]2+

This paper presents the synthesis and characterization of [Co(Fc-tpy)2](PF6)2 complex which acts as an active electrocatalyst for H2 evolution in both organic and aqueous media (Fc-tpy = 4′-ferrocenyl-2,2′:6′,2″-terpyridine). It exhibits the electrocatalytic H2 evolution in the presence of acetic acid as the proton source in (95:5 v/v) DMF/H2O medium with ≈90% of faradic efficiency in the overpotential range of 655 mV to 955 mV. The complex exhibits an ic/ip value of 65 having TOF of 825 s−1, whereas under similar condition it is 366 s−1 in case of [Co(tpy)2]2+ complex. In the presence of Fc-group in the terpyridine moiety of [Co(Fc-tpy)2]2+ the overpotential decreases up to 200 mV as compared to the [Co(tpy)2]2+ complex due to the electron donating effect of ferrocene. The mechanistic and the kinetics studies have been depicted in the presence of cobaltocene and found that interaction of Co(II)–Hδ−⋯Hδ+ is the rate-determining step in the catalytic process.

Syntheses of terpyridine-pyridylbenzothiazole linked ditopic ligands and their copper(II) complexes

New binary ligands consisting of 2,2′:6′,2″-terpyridine and 2-(2-pyridyl)benzothiazole linked with polymethylene chains of various lengths (3a-d, n = 4–11, where n is the number of CH2 units) were synthesized. Cu(II) complexes of these ligands with both CuLCl2 (4a-d) and CuL2ClO4 (5a-d) composition were also synthesized. Single crystals of the chloride complex 4b and perchlorate complex 5b were obtained, and their crystal structures were determined using X-ray diffraction. Both compounds are mononuclear Cu(II) coordination compounds with five-coordinate distorted tetragonal pyramidal geometry in the chloride complex and six-coordinate octahedral geometry in the perchlorate complex. Only terpyridine moieties coordinate with the copper ion, while pyridylbenzothiazole fragments do not participate in the coordination. Cyclic voltammograms of complexes 4 and 5 showed a Cu(II) → Cu(I) reduction at approximately −0.15 V; the observed oxidation and reduction potentials were almost identical for complexes with (CH2)4 and (CH2)11 linkers. Complex 5b, based on cyclic voltammetry data, could be turned into a heteronuclear Rh(III)–Cu(II) complex by treatment with [S-(11-(4-([2,2′:6′,2″-terpyridin]-4′-yl)phenoxy)undecyl)ethanethioate]rhodium(III) trichloride.