Connecting BINOL and terpyridine: the electronic effects of the linkage

1,1′-Bi-2-naphthol and terpyridine are covalently connected either directly or through different linkers. It is found that in contrast to the directly connected one, when the saturated methyleneoxy linker is used, there is inefficient electronic communication between the BINOL and terpyridine units and the fluorescence of the BINOL unit cannot be completely quenched by the coordination of terpyridine unit with a Cu²⁺ ion. However, a phenylene linker allows an efficient electronic communication between the BINOL and terpyridine units and the fluorescence of the BINOL is almost completely quenched upon Cu²⁺ coordination. The interaction of these compounds with valinol is studied and large fluorescence enhancements are observed for those with efficient electronic communication between the BINOL and terpyridine units.     

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.     

三联吡啶化合物的溶剂致荧光变色及丁醇异构体鉴别

在三联吡啶分子中引入N,N-二甲基官能团, 实现了三联吡啶分子的局部激发态发光. 研究发现, 溶剂的极性诱导三联吡啶的偶极矩发生变化, 实现了从深蓝光(λ_max=384 nm)到黄光(λ_max=558 nm)的溶剂致荧光变色. 由于三联吡啶的荧光易受醇溶剂中—OH基团振荡猝灭, 不同空间位阻的正丁醇、 异丁醇、 仲丁醇及叔丁醇溶剂使得三联吡啶发光光色相近, 但发光强度的差异较大. 三联吡啶进一步与ZnCl₂配位得到了三联吡啶-Zn(Ⅱ)配合物, 金属离子Zn(Ⅱ)的配位作用促进了三联吡啶分子内电荷转移. 由于电子给体N,N-二甲基官能团可发生平面扭曲, 丁醇异构体可调节三联吡啶-Zn(Ⅱ)的局部激发态和扭曲分子内电荷转移发光, 进而实现其在丁醇异构体溶剂中发光光色的调节. 因此, 三联吡啶和三联吡啶-Zn(Ⅱ)具有良好的溶剂致荧光变色性能, 可应用于4种丁醇异构体的鉴别.     

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.     

Synthesis and Metal Complex Formation of a Bis(terpyridine) Derivative with a Phenylacetylene Framework

A new bis(terpyridine) derivative with a phenylacetylene framework was synthesized via a stepwise terpyridine construction strategy. The addition of ZnCl₂ to a solution of the bis(terpyridine) in chloroform resulted in UV/vis and ¹H NMR spectral changes because of complex formation.     

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 ).     

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.     

Catalytic and asymmetric cyclopropanation of alkenes catalysed by rhenium(I) bipyridine and terpyridine tricarbonyl complexes

Re(I) tricarbonyl bipyridine and terpyridine complexes catalyse stereospecific cyclopropanation of alkenes; high selectivity of cyclopropane vs coupling and an ee of 73% and 62% for cis- and trans-cyclopropanes of styrene respectively were achieved with the [Re(L)(CO)(3)(MeCN)]OTf complex (L = chiral C(2)-symmetric terpyridine ligand).     

Expanding the supramolecular polymer LEGO system: Nitroxide‐mediated living free‐radical polymerization as a tool for mono‐ and telechelic polystyrenes

Nitroxide‐mediated, controlled living radical polymerization was employed to introduce terpyridine ligands at one or two chain ends of polystyrene. For this purpose, a unimolecular initiator bearing both a terpyridine ligand as well as a mediating nitroxide was synthesized and used for the controlled polymerization of styrene. Moreover, a maleimide‐functionalized terpyridine was prepared in order to synthesize telechelic polymers, utilizing nitroxide substitution reactions. Kinetic studies of the polymerization of styrene were carried out. In all polymerizations, special attention was focused on the retention of end‐group functionality, in light of the effects of autoinitiation and autopolymerization. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4016–4027, 2004     

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     

Polystyrene with Pendant Mixed Functional Ruthenium(II)‐Terpyridine Complexes

A vinyl substituted 2,2′:6′,2″‐terpyridine and a mixed, bifunctional ruthenium(II)‐terpyridine complex bearing a vinyl and a hydroxymethyl group are utilized as comonomers for radical copolymerization with styrene. The resulting polymers are characterized by means of UV‐vis spectroscopy and gel permeation chromatography, coupled with an in‐line diode array spectrophotometer.     

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     

Efficient route to hybrid polypyridine–carboxylate ligands for lanthanide complexation

An efficient methodology for the preparation of aminobutyl-bromo-terpyridine is described using a preformed imine prepared from a gem-dibromomethyl terpyridine derivative and the primary amine and further reduced to the secondary amine. Alkylation with pyridine, bipyridine, or terpyridine residues in the presence of a mineral base provides highly functionalized asymmetrical and symmetrical N-heterocyclic ligands. All bromo-containing products were subjected to a carboalkoxylation/hydrolysis sequence of reactions, providing the desired carboxylic acids. Stable Eu complexes were prepared under neutral aqueous conditions and some of them display interesting spectroscopic properties.     

Unique emission from norbornene derived terpyridine--a selective chemodosimeter for G-type nerve agent surrogates

A new chemodosimeter for a G-type agent that exploits norbornene derived terpyridine (NDT)-lanthanide unique emission is reported. The unusual emission between terpyridine and norbornene motifs of NDT is attributed to the significant difference in the position of the HOMO and LUMO wave functions that prevents the non-radiative relaxation pathway. An interesting magenta emission from NDT along with Eu(III) is utilized as a new fluorometric chemodosimeter that selectively detects (by changing the observed magenta emission to blue) G-type agent surrogates. A detection limit of 40 ppb is obtained and the selectivity for reactive surrogates over a variety of other close chemical analogs is demonstrated.     

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.     

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.     

联三吡啶配体及其衍生物合成进展

金属-配体间的配位作用是超分子化学中最重要的相互作用之一, 寡聚吡啶配体可以与许多过渡金属离子配位, 形成具有独特磁、光物理和电化学性质的过渡金属络合物, 因此联三吡啶配体的合成及其过渡金属络合物性能研究引起化学家的广泛关注. 综述了联三吡啶配体及其衍生物的合成方法, 主要包括成环缩合反应、过渡金属催化的偶联反应以及其它方法, 并选取具有代表性的实例对联三吡啶配体的结构和合成方法进行详细地阐述.