Terpyridine-based Ligands Research Articles

Co-Assembled Supramolecular Nanostructure of Platinum(II) Complex through Helical Ribbon to Helical Tubes with Helical Inversion.

We demonstrated the morphology transformation of co-assemblies based on terpyridine-based ligands (1R and 1S) possessing R- or S-alanine analogues and their platinum(II) complex (2R-Pt and 2S-Pt). The right-handed helical ribbon of the co-assembly formed with 0.5 equivalents of 2R-Pt to 1R was converted into the left-handed helical ribbon with 0.6 equivalents of 2R-Pt. The left-handed helical ribbon structure of the co-assembly became a tubular structure in the presence of 0.8-1.0 equivalents of 2R-Pt. The morphology transformation via helical inversion at the supramolecular level was due to an orientation change of the amide groups caused by non-covalent Pt⋅⋅⋅Pt interactions between the terpyridine of 2R-Pt and that of 2R-Pt. This study provides insights into controlling the morphology of the transformation of helical ribbons into tubular structures through helicity inversion in co-assembled supramolecular nanostructures based on platinum(II) complexes.

Cyclometalated Ir(III) Complexes Involving Functionalized Terpyridine-Based Ligands Exhibiting Aggregation-Induced Emission and Their Potential Applications in CO2 Detection

Synthesis of three novel terpyridine-based donor–acceptor (D-A) ligands (TP1, TP2, TP3) and cyclometalated iridium complexes [Ir(ppy)2TP1]+PF6– (C1), [Ir(ppy)2TP2]+PF6– (C2), and [Ir(ppy)2TP3]+PF6– (C3) [ppy = 2−phenyl pyridine] involving these were described. The ligands and complexes were characterized by spectroscopic studies (1H, 13C, 19F, 31P, ESI-MS, UV-vis, and fluorescence). Crucial role of intermolecular interactions in aggregation-caused quenching (ACQ; C2) and aggregation-induced emission (AIE; C3) was rationalized by X-ray single-crystal analyses. Vital role of restricted intramolecular rotation (RIR) in inducing AIE upon aggregation via π–π interactions in these complexes was scrutinized by various studies. Because of strong intramolecular charge transfer these D−A based AIEgens exhibited solvatochromism. Further, AIE property of the complexes C1 and C3 was exploited toward detection of CO2.

Ligand Impact on Monolayer Electrochromic Material Properties.

In this study, we present a range of efficient highly durable electrochromic materials that demonstrate excellent redox and lifetime stability, sufficient coloration contrast ratios, and the best-in-class electron-transfer constants. The materials were formed by anchoring as little as a monolayer of predefined iron complexes on a surface-enhanced conductive solid support. The thickness of the substrate was optimized to maximize the change in optical density. We demonstrate that even a slight change in molecular sterics and electronics results in materials with sufficiently different properties. Thus, minor changes in the ligand design give access to materials with a wide range of color variations, including green, purple, and brown. Moreover, ligand architecture dictates either orthogonal or parallel alignment of corresponding metal complexes on the surface due to mono- or bis-quaternization. We demonstrate that monoquaternization of the complexes during anchoring to the surface-bound template layer results in redshifts of the photoabsorption peak. The results of in-solution bis-methylation supported by density functional theory calculations show that the second quaternization may lead to an opposite blueshift (in comparison with monomethylated analogs), depending on the ligand electronics and the environmental change. It is shown that the variations of the photoabsorption peak position for different ligands upon attachment to the surface can be related to the calculated charge distribution and excitation-induced redistribution. Overall, the work demonstrates a well-defined method of electrochromic material color tuning via manipulation of sterics and electronics of terpyridine-based ligands.

Multicomponent Self-Assembly of Metallo-Supramolecular Macrocycles and Cages through Dynamic Heteroleptic Terpyridine Complexation.

Spontaneous formation of the heteroleptic cadmium(II) bis(terpyridine) complex under ambient conditions can be achieved by a combination of 6,6''-di(2,6-dimethoxylphenyl)-substituted and unsubstituted terpyridine-based ligands. Building on this dynamic heteroleptic complexation, diverse metallo-supramolecular macrocycles and cages were readily assembled in quantitative yields from the predesigned multicomponent systems. The complementary ligation reinforced self-recognition to facilitate the shape-dependent self-sorting of a four-component dynamic library into two well-defined parallelograms. In addition, the subtle lability difference between homoleptic and heteroleptic complexes led to the site-selective CdII -ZnII transmetalation in the Sierpiński triangle. Facile construction of a dodecanuclear tetrahedral metallocage was also realized by using two self-recognizable tritopic building blocks. The photophysical study of the metallo-supramolecules assembled from the d10 metal ions revealed intense ligand-based photoluminescence in solution. The self-assembly strategy described here provides an efficient methodology for building pre-programmable, sophisticated supramolecular architectures furnished with photoactivity.

Synthesis, characterization and using a new terpyridine moiety-based ion-imprinted polymer nanoparticle: sub-nanomolar detection of Pb(II) in biological and water samples

A highly selective lead-imprinted polymer was synthesized via a thermal precipitation polymerization technique based on a terpyridine-based ligand as the complexing agent. The synthesized polymer was successfully incorporated in a graphite paste electrode (GPE) as the recognition element for lead ion (Pb2+). Differential pulse anodic stripping voltammetry (DPASV) technique was used to transduce the binding events at the modified electrode. The imprinted polymer nanoparticles (IP-NPs) were synthesized by precipitation polymerization of ethylene glycol dimethacrylate as the cross-linker, 2,2′-azobisisobutyronitrile as the free radical initiator and 2,2′:6′,6″-terpyridine (terpy) as the recognition element. The sensing procedure is based on the accumulation of lead ions at − 1.0 V vs. Ag/AgCl. Afterward, the DPV was recorded by the sweeping potential in a positive direction to oxidize the accumulated ions, leading to the appearance of a significant anodic peak. The constructed IIP–GPE revealed a linear response toward Pb2+ over the concentration range from 0.4 to 10 nM (with the sensitivity of 693.95 nA nM−1 cm−2) and 10 nM to 1.0 µM (with the sensitivity of 580.25 µA µM−1 cm−2). The limit of detection (LOD) was evaluated to be 0.11 nM (for S/N = 3). The accuracy of the sensor was explored by analysis of a quality control material (QCMs, Seronorm™ urine REF NO 1011645) and different water samples. Selectivity studies showed no particular interference for detection of Pb(II).

Different Origins of Strain-Induced Chirality Inversion of Co2+-Triggered Supramolecular Peptide Polymers

We report a distinctly different dynamic helix inversion pathway of self-assembled terpyridine-based ligands composed of different numbers of peptide moieties with Co2+ and its amplification of strain-induced chirality from an achiral terpyridine moiety. The helical chirality of the metal centers, coordinated by terpyridine ligands, is controlled by strain-induced chirality with complex ligand-to-Co2+ ratios. We also show that the distinct helical inversion mechanism is significantly dependent on the number of peptides attached to ligands. The helical inversion pathway of the self-assembled ligand (R-1 and S-1) complexes composed of one alanine analogue (R- or S-2-amino-1-propyl moiety) and one long saturated alkyl chain relies on two steps of chirality with different complex geometries, first from strain-induced chirality originating from an octahedral structure to octahedral structure with different helical direction and then on to helical chirality in a square-pyramidal structure. In contrast, the heli...

Facile Construction of Metallo-supramolecular Poly(3-hexylthiophene)-block-Poly(ethylene oxide) Diblock Copolymers via Complementary Coordination and Their Self-Assembled Nanostructures

Complementary coordination of two predesigned 2,2':6',2″-terpyridine-based ligands to a ZnII ion led to the exclusive formation of a heteroleptic bis(terpyridine) complex under ambient conditions. This highly self-selective process was facilitated by 9-anthracenyl substituents at the 6,6″-positions of a terpyridine, which not only decelerated the formation rate of its homoleptic complex, but also provided π-stacking stabilization in the heteroleptic complex. Facile construction of metallo-supramolecular poly(3-hexylthiophene) (P3HT)-block-poly(ethylene oxide) (PEO) diblock copolymers was realized using the complementary ligand pair. The morphological studies of the amphiphilic block copolymers in solution were conducted by atomic force microscopy and transmission electron microscopy, indicating that the self-assembled core-shell morphology such as spherical and fibrillar nanostructures could be controlled by adjusting the rod-coil block ratios. The heteroleptic complexes residing at the junction between two polymer blocks could be readily dissociated by EDTA to afford the unshelled P3HT nanofiber networks, and restored by treatment of bifunctional ZnII-terpyridine-capped PEO to redisperse the aggregates. The presented supramolecular methodology highlights the merits of complementary metal-ligand coordination, and offers a new approach to engineering nanostructures assembled from rod-coil block copolymers.

Synthesis of two Zn(II) compounds from terpyridine-based ligand: Structures, crystal-to-crystal transformation and detection of nerve agent mimics

Reactions of ZnCl2 with 4′-(2,4-disulfophenyl)-2,2′:6′2″-terpyridine (H2DSPT) result to two new compounds with formula, {[Zn(DSPT)(H2O)2]·2H2O}n (1) and {[Zn(DSPT)(H2O)2]·H2O}n (2), respectively. Compound 1 is a binuclear complex, whereas compound 2 is a mononuclear organozinc compound. The coordination compounds can be controllable synthesized by adjust the pH value. The thermal behavior of 1 was explored by TG and VT-PXRD, which indicated that it undergo crystal-to-crystal transformation manner. Both compounds 1 and 2 show weak luminescence in both solid state and water emulsions compared with H2DSPT. The luminescence intensity of compound 1 can strongly enhanced by the addition of diethylchlorophosphonate (DCP), but significant less influenced by dimethylmethylphosphonate (DMMP), diethylcyanophosphonate (DCNP) and other selected organophosphate, which make compound 1 has potential application on nerve-agent detection.

Formation and properties of a terpyridine-based 2D MOF on the surface of water

Two-dimensional networks inspired by graphene are of prime importance in nanoscience. We present a computational study of an infinite molecular sheet confined on a water surface to assess its properties and formation mechanism. Terpyridine-based ligand molecules are interlinked by Zn ions to form an extended 2D metal-organic framework. We show that the network is stable on the water surface, and that the substrate affects the dynamic properties of the sheet, exhibiting a confining effect and flattening the sheet by 30%. We use metadynamics to characterize the process of network formation and breaking and determine an intra-network binding energy of 143 kJ mol−1. Based on this mechanistic insight we propose that the 2D network strength can be tuned by varying the rigidity of the ligand through its chemical structure.

Metallo-Supramolecular Self-Assembly of a Multicomponent Ditrigon Based on Complementary Terpyridine Ligand Pairing.

Predesigned complementary complexation of two 2,2':6',2″-terpyridine-based ligands was established by installing 2,6-dimethoxyphenyl substituents at the terpyridyl 6,6″-positions, which provided ancillary ion-dipole interactions in the coordination process and extra π-stacking stabilization in the resultant heteroleptic complex. The high-fidelity self-recognition ligation afforded facile access to the quantitative self-assembly of multicomponent triangle [Cd6L(3)3L(4)3] and ditrigon [Cd15L(3)6L(5)3] (that is, a hexagon with six 120° angles and two alternating edge lengths). It was found that the linear 6,6″-substituted ditopic motif (L(3)) would be directed by the ligand geometry of L(5) to selectively incorporate into the parallel homoleptic connections in the bilayered framework.

Static and dynamic binding behavior of an IgG2 monoclonal antibody with several new mixed mode affinity adsorbents

The binding behavior of several mixed-mode chromatographic adsorbents, derived from different terpyridine-based ligands immobilized onto Sepharose FF™, has been investigated with a humanized IgG2 monoclonal antibody. Static adsorption isotherms were determined and the derived parameters used to guide the choice of ligand structure and adsorption conditions to achieve favorable IgG2 mAb binding under dynamic loading conditions. The binding and elution behavior of selected adsorbents in packed chromatographic columns were studied with the purified IgG2 mAb and crude cell culture broths containing the same IgG2 mAb. Clearance of host cell proteins was found to be strongly influenced by the structure of the ligand used to generate these mixed mode resins. One ligand candidate in particular, ES-(Cl.S.Cl)terpy, was found to possess selectivity on a par with the traditionally employed Protein A affinity adsorbents for the purification of monoclonal IgG2s with an excellent level of clearance of host cell proteins. Moreover, high binding capacities, e.g. between 34 and 70 mg IgG2 mAb/mL resin, were achieved with these new adsorbents.

Studies on the binding sites of IgG2 monoclonal antibodies recognized by terpyridine-based affinity ligands.

This investigation has examined the origin of the molecular recognition associated with the interaction of monoclonal IgG2's with terpyridine-based ligands immobilized onto agarose-derived chromatographic adsorbents. Isothermal titration calorimetric (ITC) methods have been employed to acquire thermodynamic data associated with the IgG2-ligand binding. These ITC investigations have documented that different enthalpic and entropic processes are involved depending on the nature of the chemical substituents in the core structure of the terpyridinyl moiety. In addition, molecular docking studies have been carried out with IgG2 structures with the objective to identify possible ligand binding sites and key interacting amino acid residues. These molecular docking experiments with the different terpyridine-based ligands have shown that all of the examined ligands can potentially undergo favorable interactions with a site located within the Fab region of the IgG2. However, another favorable binding site was also identified from the docking poses to exist within the Fc region of the IgG2 for some, but not all, of the ligands studied. These investigations have provided a basis to elucidate the unique binding properties and chromatographic behaviors shown by several substituted terpyridine ligands in their interaction with IgGs of different isotype. Copyright © 2016 John Wiley & Sons, Ltd.

Synthesis, structure, and properties of a 3D porous Zn(ii) MOF constructed from a terpyridine-based ligand

A new Zn MOF has been synthesized based on a terpyridine-based ligand, which exhibits selective fluorescent sensing properties for metal ions and nitroaromatic compounds, especially Fe3+, 4-NPH and 4-NP.

Rhenium(I) terpyridine complexes - synthesis, photophysical properties and application in organic light emitting devices.

Six new Re(i) complexes of the general formula [ReCl(CO)3(4'-R-terpy-κ(2)N)] with 2,2':6',2''-terpyridine-based ligands have been synthesized and characterized by IR, NMR ((1)H and (13)C), UV-Vis spectroscopy and single crystal X-ray analysis. The luminescent properties of [ReCl(CO)3(4'-R-terpy-κ(2)N)] were studied in solution and solid state, at 298 and 77 K, respectively. To obtain detailed insight into the electronic structures and spectroscopic properties of [ReCl(CO)3(4'-R-terpy-κ(2)N)], the density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations were performed. Also, the suitability of this class of materials for being applied in organic light emitting diodes (OLEDs) has been preliminarily tested.

A novel D-A type terpyridine-based carbazole Zn(II) complex with enhanced two-photon absorption and its bioimaging application

A novel 2,2′:6′,2″-terpyridine-based ligand L and its Zn(II) complex [ZnL2](PF6)2 were designed, synthesized and fully characterized. The crystal structures of L and [ZnL2](PF6)2 were confirmed by single crystal X-ray diffraction analysis. Photophysical optical properties of the ligand and its complex were investigated systemically. The results reveal that the complex exhibits a new strong absorption band at about 400 nm compared to its free ligand, which is assigned to the intramolecular charge transfer (ICT) transitions. The complex displays lower fluorescence intensity, due to the better planarity of the ligand, higher electronic mobility, and leading to easier ICT. However, two-photon absorption (2PA) cross-sections of the complex is much enhanced than that of the free ligand in the near-infrared region (NIR). Furthermore, [ZnL2](PF6)2 can be penetrated into living cells without cell-penetrating molecular transporter, stained with cytoplasm in the NIR (830 nm). Therefore such complex is promising for further biomaging applications.

The effect of potential supramolecular-bond promoters on the DNA-interacting abilities of copper-terpyridine compounds.

Three copper(ii) coordination compounds have been prepared from three different 2,2':6',2''-terpyridine-based ligands, which have been selected to investigate the potential role of supramolecular interactions on the DNA-interacting and cytotoxicity properties of the corresponding metal complexes. Hence, the ligands 4'-((naphthalen-2-yl)methoxy)-2,2':6',2''-terpyridine () and 4'-((1H-benzo[d]imidazol-2-yl)methoxy)-2,2':6',2''-terpyridine () have been synthesized from commercially-available 4'-chloro-2,2':6',2''-terpyridine (), and their copper(ii) complexes have been obtained by reaction with copper(ii) nitrate. The DNA-interacting abilities of the corresponding compounds [Cu()(H2O)(NO3)2] (), [Cu()(NO3)(H2O)](NO3)(MeOH) () and [Cu()(NO3)(H2O)](NO3) () have been investigated using different techniques, and cytotoxicity assays with several cancer cell lines have revealed interesting features, viz. the more efficient complex is , which although it does not act as a DNA cleaver, displays the most effective DNA-interacting and cytotoxic properties, compared to and .

A turn-on fluorogenic Zn(II) chemoprobe based on a terpyridine derivative with aggregation-induced emission (AIE) effects through nanofiber aggregation into spherical aggregates.

The self-assembly of a terpyridine-based ligand in a DMSO/water solvent mixture (1 : 99 v/v) with a high content of water formed a nanofibrillar structure and showed a non-emissive process. On the other hand, the self-assembly of the terpyridine-based ligand exhibited strong emission in the presence of Zn(2+) due to the formation of coordination bonds between the terpyridine moieties and the Zn(2+) by the aggregation-induced emission effect. The morphology of this aggregate represented a spherical structure.

One-step multicomponent self-assembly of a first-generation Sierpiński triangle: from fractal design to chemical reality.

A novel terpyridine-based architecture that mimics a first-generation Sierpiński triangle has been synthesized by multicomponent assembly and features tpy-Cd(II)-tpy connectivity (tpy=terpyridine). The key terpyridine ligands were synthesized by the Suzuki cross-coupling reaction. Mixing two different terpyridine-based ligands and Cd(II) in a precise stoichiometric ratio (1:1:3) produced the desired fractal architecture in near-quantitative yield. Characterization was accomplished by NMR spectroscopy, mass spectrometry, and transmission electron microscopy.

Reversibly tunable helix inversion in supramolecular gels trigged by Co(2+).

Terpyridine-based ligands form octahedral complexes with Co(2+) at low cation concentrations to form helical assemblies which provide a supramolecular gel framework. Increasing the Co(2+) concentration above 0.6 equiv. reveals a second, co-existing square pyramidal complex derived assembly, having a distinct helicity. While this geometry dominates at 1 equiv. of Co(2+), we find this unique form of helical inversion to be fully reversible and controllable.

Synthesis, photophysical and electrochemical characterization of terpyridine-functionalized dendritic oligothiophenes and their Ru(II) complexes

Pd-catalyzed Sonogashira cross-coupling reactions were used to synthesize novel π-conjugated oligothienylene-ethynylene dendrons and their corresponding terpyridine-based ligands. Their complexation with Ru(II) led to interesting novel metallodendrimers with rich spectroscopic properties. All new compounds were fully characterized by 1H and 13C NMR, as well as MALDI–TOF mass spectra. Density functional theory (DFT) calculations performed on these complexes gave more insight into the molecular orbital distributions. Photophysical and electrochemical studies were carried out in order to elucidate structure–property relationships and the effect of the dendritic structure on the metal complexes. Photophysical studies of the complexes revealed broad absorption spectra covering from 250 to 600 nm and high molar extinction coefficients. The MLCT emission of these complexes were significantly red-shifted (up to 115 nm) compared to the parent [Ru(tpy)2]2+ complex.