Terpyridine‐modified poly(vinyl chloride): Possibilities for supramolecular grafting and crosslinking

Commercially available poly(vinyl chloride) (PVC) was covalently modified with terpyridine supramolecular binding units in a two‐step reaction. First, PVC was modified with aromatic thiols to introduce OH functionalities into the polymer backbone, which were subsequently reacted with an isocyanate‐functionalized terpyridine binding unit. The resulting functionalized material contained metal‐ion binding sites, which could be used for grafting and crosslinking reactions. A grafting experiment was performed with a small organic terpyridine ligand. The complexation of the modified PVC with several transition‐metal ions was studied with ultraviolet–visible spectroscopy and gel permeation chromatography. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2964–2973, 2003     

End‐functionalization of semiconducting species with dendronized terpyridine–Ru(II)–terpyridine complexes

Semiconducting oligomers and polymers decorated with two or one dendronized tpy‐Ru(II)‐tpy metallocomplexes are presented. Initially, free terpyridine end‐functionalized semiconducting oligomers (distyrylanthracene, quinquephenylene, mono‐ and trifluorenes) were prepared while in a second approach, atom transfer radical polymerization was employed for the preparation of side‐chain oligomeric and polymeric (oxadiazole)s using a terpyridine initiator. These terpyridine‐bearing oligomers and polymers were complexated with a Percec‐type first‐generation (G1) dendronized terpyridine–Ru(III)Cl₃ monocomplex, having two dodecyloxy groups. All oligomeric and polymeric metallocomplexes were characterized via NMR spectroscopies for their structural perfection and via UV‐Vis and PL spectroscopies for their optical properties. The existence of the organic semiconducting blocks in combination with the terpyridine–Ru(II)–terpyridine groups afforded hybrid metallo‐semiconducting species presenting the optical features of both their components. Moreover, their thin‐film morphologies were investigated through atomic force microscopy, revealing, in some cases, an organization tendency in the nanometer scale. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1939–1952, 2009     

A new terpyridine tethered polythiophene: Electrosynthesis and characterization

A novel polythiophene bearing a pendant terpyridine moiety has been synthesized by electrochemical polymerization of a new thiophene monomer, namely 4′‐(2,2′:5′,2″‐terthien‐3′‐ethynyl)‐2,2′:6′,2″‐terpyridine (TAT). The insertion of a conjugated ethynyl spacer between the terthiophene and the terpyridine fragments provides for an effective extension of the delocalization of electrons within the structural unit and the polymer as a whole. The synthesis and characterization of the relevant monomer, the electrosynthesis of the corresponding polymer and its electrochemical, UV–visible spectroelectrochemical and IR characterization are described. Finally, a comparison between the electrochemical, spectroscopic, and spectroelectrochemical properties of PTAT and the analogue, saturated‐spacer PTTT (TTT = 4′‐[(2,2′:5′,2″‐terthien‐3′‐yl)methoxy]‐2,2′:6′,2″‐terpyridine) polymer is discussed. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

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.     

A Flexible Terpyridine Derivative Interacts Specifically with G‐Quadruplexes

G‐quadruplexes formed by nucleic acids are implicated in pathologies ranging from cancers to neurodegenerative diseases. We evaluated interactions of 29 bi‐ and terpyridine derivatives with G‐quadruplexes and duplexes. FRET‐melting, circular dichroism, and ¹H NMR spectroscopy showed that one terpyridine derivative interacted very selectively with G‐quadruplexes. This G‐quadruplex ligand inhibited helicase activity and should influence G‐quadruplex‐related biological processes.     

Synthesis,characterization, and evaluation of biological activities of new 4′‐substituted ruthenium (II) terpyridine complexes: Prospective anti‐inflammatory properties

The synthesis and characterization of Ru (II) terpyridine complexes derived from 4′ functionalized 2,2′:6′,2″‐terpyridine (tpy) ligands are reported. The heteroleptic complexes comprise the synthesized ligands 4′‐(2‐thienyl)‐ 2,2′:6′,2″‐terpyridine) or (4′‐(3,4‐dimethoxyphenyl)‐2,2′:6′,2″‐terpyridine and (dimethyl 5‐(pyrimidin‐5‐yl)isophthalate). The new complexes [Ru(4′‐(2‐thienyl)‐2,2′:6′,2″‐terpyridine)(5‐(pyrimidin‐5‐yl)‐isophthalic acid)Cl₂] ( 9 ), [Ru(4′‐(3,4‐dimethoxyphenyl)‐2,2′:6′,2″‐terpyridine)(5‐(pyrimidin‐5‐yl)‐isophthalic acid)Cl₂] ( 10 ), and [Ru(4′‐(2‐thienyl)‐2,2′:6′,2″‐terpyridine)(5‐(pyrimidin‐5‐yl)‐isophthalic acid)(NCS)₂] ( 11 ) were characterized by ¹H‐ and ¹³C‐NMR spectroscopy, C, H, N, and S elemental analysis, UPLC‐ESI‐MS, TGA, FT‐IR, and UV‐Vis spectroscopy. The biological activities of the synthesized ligands and their Ru (II) complexes as anti‐inflammatory, antimicrobial, and anticancer agents were evaluated. Furthermore, the toxicity of the synthesized compounds was studied and compared with the standard drugs, namely, diclofenac potassium and ibuprofen, using hemolysis assay. The results indicated that the ligands and the complex 9 possess superior anti‐inflammatory activities inhibiting albumin denaturation (89.88–100%) compared with the standard drugs (51.5–88.37%) at a concentration of 500 μg g^?1. These activities were related to the presence of the chelating N‐atoms in the ligands and the exchangeable chloro‐ groups in the complex. Moreover, the chloro‐ and thiophene groups in complex 9 produce a higher anticancer activity compared with its isothiocyanate derivative in the complex 11 and the 3,4‐dimethoxyphenyl moiety in complex 10 . Considering the toxicity results, the synthesized ligands are nontoxic or far less toxic compared with the standard drugs and the metal complexes. Therefore, these newly synthesized compounds are promising anti‐inflammatory agents in addition to their moderate unique broad antimicrobial activity.     

Facile Self‐Assembly of Metallo‐Supramolecular Ring‐in‐Ring and Spiderweb Structures Using Multivalent Terpyridine Ligands

A series of metallo‐supramolecular ring‐in‐ring structures was generated by assembling Cd^II ions and the multivalent terpyridine ligands ( L^1‐3 ) composed of one 60°‐bent and two 120°‐bent bis(terpyridine)s with varying alkyl linker lengths. The mechanistic study for the self‐assembly process excluded an entropically templated pathway and showed that the intramolecularly complexed species is the key intermediate leading to ring‐in‐ring formation. The next‐generation superstructure, a spiderweb, was produced in quantitative yield using the elongated decakis(terpyridine) ligand ( L⁵ ).     

Playing LEGO with macromolecules: Design,synthesis, and self‐organization with metal complexes

Several synthetic strategies for the incorporation of supramolecular binding units into polymers are described. Specifically, terpyridine ligands have been introduced into polymers in such a way that they are distributed either randomly throughout the polymer backbone or at the chain end(s). Two terpyridine ligands form octahedral complexes with a variety of transition‐metal ions, each having different properties. Some general statements regarding metal complex stability are presented as well as a special case representing the selective construction of heteroleptic terpyridine complexes. This leads to a kind of LEGO system for connecting and disconnecting the polymer blocks via metal complexes. Metallo‐supramolecular block copolymers, graft copolymers, and chain‐extended polymers can be designed and prepared with the principles described. Once the design parameters have been derived, thorough control over the final material and its properties can be gained. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1413–1427, 2003     

Terpyridine–Porphyrin Hetero‐Pacman Compounds

The two different coordination spheres afforded by Pacman architectures offer cooperativity derived from two different metal centers. A modular strategy is developed to produce a hetero‐Pacman scaffold featuring a porphyrin and terpyridine for metal‐ion binding. A double Suzuki reaction was employed to first attach a terpyridine moiety to a xanthene backbone and then attach a porphyrin. The new hetero‐Pacman scaffold has been characterized and all building blocks have been isolated and structurally characterized. The principle objective to incorporate different metal centers was confirmed by isolating a trinuclear complex comprising two porphyrinic units and a bis(terpyridine)–iron unit. The compounds described herein expand the Pacman scaffold concept by allowing for the incorporation of a terpyridine–metal complex proximate to a porphyrin‐cofactor active site for small‐molecule activation.     

Side‐chain terpyridine polymers through atom transfer radical polymerization and their ruthenium complexes

Polymers containing side‐chain terpyridine ligands of well‐defined architectures and controllable molecular weights and molecular weight distributions are reported. These polymers were synthesized by the atom transfer radical polymerization (ATRP) of a newly synthesized terpyridine monomer with three functional initiators. The obtained polymers were characterized with ¹H NMR and gel permeation chromatography techniques. The efficiency of the ATRP technique and the overall control of the molecular characteristics of the polymers were demonstrated by a kinetic study of the polymerization reaction. Subsequently, the ruthenium(III)/ruthenium(II) complexation chemistry was employed for the attachment of bis(dodecyloxy)‐functionalized terpyridine moieties onto each side 2,2′:6′,2″‐terpyridine unit of the main polymeric backbone. Thus, the grafting approach was successfully combined with the metal–ligand coordination chemistry for the preparation of highly soluble polymeric complexes. The resulting complexes were fully characterized by means of ¹H NMR, gel permeation chromatography, and ultraviolet–visible spectroscopy. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4838–4848, 2005     

Iron in a Cage: Fixation of a Fe(II)tpy2 Complex by Fourfold Interlinking

The coordination sphere of the Fe(II) terpyridine complex 1 is rigidified by fourfold interlinking of both terpyridine ligands. Profiting from an octa‐aldehyde precursor complex, the ideal dimensions of the interlinking structures are determined by reversible Schiff‐base formation, before irreversible Wittig olefination provided the rigidified complex. Reversed‐phase HPLC enables the isolation of the all‐trans isomer of the Fe(II) terpyridine complex 1 , which is fully characterized. While temperature independent low‐spin states were recorded with superconducting quantum interference device (SQUID) measurements for both, the open precursor 8 and the interlinked complex 1 , evidence of the increased rigidity of the ligand sphere in 1 was provided by proton T₂ relaxation NMR experiments. The ligand sphere fixation in the macrocyclized complex 1 even reaches a level resisting substantial deformation upon deposition on an Au(111) surface, as demonstrated by its pristine form in a low temperature ultra‐high vacuum scanning tunneling microscope experiment.     

Reversible Assembly of Microgels by Metallo‐Supramolecular Chemistry

The combination of supramolecular chemistry and soft colloids as microgels represents an ambitious way to develop multi‐versatile colloidal assemblies. Hereafter, terpyridine‐functionalized poly(N‐isopropylacrylamide) (PNiPAM) microgel building blocks are shown to undergo an assemble–freeze–disassemble process. The microgel assemblies, which are controlled by monitoring the attractive and repulsive potentials between the soft colloidal particles, are then frozen by forming inter‐particle metal–terpyridine bis‐complexes upon addition of the metallic cation (such as Fe^II, Co^II). By oxidation of the metal–terpyridine bis‐complex links, the aggregates open up, which is due to the complex dissociation releasing the connected particles in the form of single microgels. We extended our work to the development of 1D filaments and 2D membranes materials made of soft particles connected via supramolecular chemistry.     

Functionalized oligomers and copolymers with metal complexing segments: a simple and high yield entry towards 2,2′:6′,2″‐terpyridine monofunctionalized telechelics

4′‐Chloro‐2,2′:6′,2″‐terpyridine was reacted in a high yield Williamson type reaction with α‐hydroxy‐ω‐carboxy‐functionalized poly(ethylen‐oxide) to obtain monoterpyridine terminated telechelics. The completeness of the functionalization was proven by NMR, GPC and MALDI‐TOF‐MS investigations. Addition of transition metal ions resulted in the formation of the corresponding octahedral terpyridine metal complexes and resulted in the formation of metallo‐supramolecular dimers.     

4,4′′′′‐Azobis[2,2′: 6′,2″‐terpyridine] and its Metal Complexes

By two different routes, 4,4′′′′‐azobis[2,2′: 6′,2″‐terpyridine] was synthesized. Its ruthenium complexes show interesting metal‐to‐ligand charge transfer (MLCT) absorption maxima in the electronic spectra. They represent the first ruthenium complexes of terpyridine units to give blue solutions.     

Functionalized polymers with metal complexing segments: a simple and high‐yield entry towards 2,2′:6′,2″‐terpyridine‐based oligomers

Williamson type ether reactions were utilized for a high yield reaction of 4′‐chloro‐2,2′:6′,2″‐terpyridine with α,ω‐dihydroxy‐functionalized poly(ethylene oxide) and poly(oxytetramethylene)s to obtain bis(terpyridine)‐terminated telechelics. The completeness of the functionalization was proven by NMR spectroscopy, GPC and MALDI‐TOF‐MS investigations. The addition of transition metal ions resulted in a polyaddition polymerization leading to the formation of extended metallo‐supramolecular polymers, as proven by UV/VIS spectroscopy titration experiments.     

Metallo‐Supramolecular Graft Copolymers: A Novel Approach Toward Polymer‐Analogous Reactions

A copolymer of poly(methyl methacrylate) with terpyridine units in the side chains was synthesized utilizing free‐radical polymerization. The free terpyridine units were complexed with several different terpyridineruthenium mono‐complexes, yielding metallo‐supramolecular graft copolymers. The materials obtained were characterized by means of NMR and UV‐vis spectroscopy as well as GPC. Characterization by thermal analysis revealed distinct differences between these new materials and the initial copolymer.     

Remarkable Tuning of the Coordination and Photophysical Properties of Lanthanide Ions in a Series of Tetrazole‐Based Complexes

A series of seven new tetrazole‐based ligands (L1, L3–L8) containing terpyridine or bipyridine chromophores suited to the formation of luminescent complexes of lanthanides have been synthesized. All ligands were prepared from the respective carbonitriles by thermal cycloaddition of sodium azide. The crystal structures of the homoleptic terpyridine–tetrazolate complexes [Ln(Li)₂]NHEt₃ (Ln=Nd, Eu, Tb for i=1, 2; Ln=Eu for i=3, 4) and of the monoaquo bypyridine–tetrazolate complex [Eu(H₂O)(L7)₂]NHEt₃ were determined. The tetradentate bipyridine–tetrazolate ligand forms nonhelical complexes that can contain a water molecule coordinated to the metal. Conversely, the pentadentate terpyridine–tetrazolate ligands wrap around the metal, thereby preventing solvent coordination and forming chiral double‐helical complexes similarly to the analogue terpyridine–carboxylate. Proton NMR spectroscopy studies show that the solid‐state structures of these complexes are retained in solution and indicate the kinetic stability of the hydrophobic complexes of terpyridine–tetrazolates. UV spectroscopy results suggest that terpyridine–tetrazolate complexes have a similar stability to their carboxylate analogues, which is sufficient for their isolation in aerobic conditions. The replacement of the carboxylate group with tetrazolate extends the absorption window of the corresponding terpyridine‐ (≈20 nm) and bipyridine‐based (25 nm) complexes towards the visible region (up to 440 nm). Moreover, the substitution of the terpyridine–tetrazolate system with different groups in the ligand series L3–L6 has a very important effect on both absorption spectra and luminescence efficiency of their lanthanide complexes. The tetrazole‐based ligands L1 and L3–L8 sensitize efficiently the luminescent emission of lanthanide ions in the visible and near‐IR regions with quantum yields ranging from 5 to 53 % for Eu^III complexes, 6 to 35 % for Tb^III complexes, and 0.1 to 0.3 % for Nd^III complexes, which is among the highest reported for a neodymium complex. The luminescence efficiency could be related to the energy of the ligand triplet states, which are strongly correlated to the ligand structures.     

The LEGO toolbox: Supramolecular building blocks by nitroxide‐mediated controlled radical polymerization

A terpyridine‐functionalized alkoxyamine unimolecular initiator was used for the nitroxide‐mediated controlled living radical polymerization of n‐butylacrylate, N,N‐dimethylacrylamide, 4‐vinylpyridine, 2‐vinylpyridine, and isoprene. For the former three monomers, the kinetics were studied. All polymerizations resulted in well‐defined polymers having a single terpyridine ligand at the chain end and narrow polydispersity indices. The obtained polymers are valuable building blocks for metallo‐supramolecular polymers. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6331–6344, 2005     

Surface‐Junction Effects on Interfacial Electron Transfer between Bis(terpyridine)iron(II) and Hydrogen‐Terminated Silicon(111) Electrode

Interfacial electron transfer at bis(tpy)–iron(II) complexes (tpy=2,2′:6′,2′′‐terpyridine) on Si(111) electrodes was investigated by using four types of surface‐anchor terpyridine ligands. Despite the greater distance, electron transfer between the bis(tpy)–iron(II) unit and the electrode is accelerated in surface‐anchor ligands with an additional phenylene group.     

Synthesis of dendronized polymer brushes containing metallo‐supramolecular polymer side chains

A new kind of dendronized polymer brush with metallo‐supramolecular polymer side chains was fabricated by a combination of macromonomer and graft‐to approach. The alternating copolymers of maleic anhydride and styryl macromonomers pendant with Fréchet‐type dendrons of three generations were reported previously. In this article, terpyridine groups were introduced along the backbone of the dendronized polymers through the amidolysis of anhydride groups. The terpyridine functionalized PEO linear chains were then incorporated through the complexation of terpyridine and Ru(II) ion. Thus, dendronized polymer brushes with amphiphilic properties were synthesized. AFM analysis showed worm‐like single molecular morphologies of the polymers of three generations, and ¹H NMR analysis indicated that such molecular brushes had an amphiphilic nature in solution. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3303–3310, 2007