Excited State Tuning of Bis(tridentate) Ruthenium(II) Polypyridine Chromophores by Push–Pull Effects and Bite Angle Optimization: A Comprehensive Experimental and Theoretical Study

The synergy of push–pull substitution and enlarged ligand bite angles has been used in functionalized heteroleptic bis(tridentate) polypyridine complexes of ruthenium(II) to shift the ¹MLCT absorption and the ³MLCT emission to lower energy, enhance the emission quantum yield, and to prolong the ³MLCT excited‐state lifetime. In these complexes, that is, [Ru(ddpd)(EtOOC‐tpy)][PF₆]₂, [Ru(ddpd‐NH₂)(EtOOC‐tpy)][PF₆]₂, [Ru(ddpd){(MeOOC)₃‐tpy}][PF₆]₂, and [Ru(ddpd‐NH₂){(EtOOC)₃‐tpy}][PF₆]₂ the combination of the electron‐accepting 2,2′;6′,2′′‐terpyridine (tpy) ligand equipped with one or three COOR substituents with the electron‐donating N,N′‐dimethyl‐N,N′‐dipyridin‐2‐ylpyridine‐2,6‐diamine (ddpd) ligand decorated with none or one NH₂ group enforces spatially separated and orthogonal frontier orbitals with a small HOMO–LUMO gap resulting in low‐energy ¹MLCT and ³MLCT states. The extended bite angle of the ddpd ligand increases the ligand field splitting and pushes the deactivating ³MC state to higher energy. The properties of the new isomerically pure mixed ligand complexes have been studied by using electrochemistry, UV/Vis absorption spectroscopy, static and time‐resolved luminescence spectroscopy, and transient absorption spectroscopy. The experimental data were rationalized by using density functional calculations on differently charged species (charge n=0–4) and on triplet excited states (³MLCT and ³MC) as well as by time‐dependent density functional calculations (excited singlet states).     

Molecular Ruby under Pressure

The intensely luminescent chromium(III) complexes [Cr(ddpd)₂]³⁺ and [Cr(H₂tpda)₂]³⁺ show surprising pressure‐induced red shifts of up to ?15 cm^?1 kbar^?1 for their sharp spin‐flip emission bands (ddpd=N,N′‐dimethyl‐N,N′‐dipyridine‐2‐yl‐pyridine‐2,6‐diamine; H₂tpda=2,6‐bis(2‐pyridylamino)pyridine). These shifts surpass that of the established standard, ruby Al₂O₃:Cr³⁺, by a factor of 20. Beyond the common application in the crystalline state, the very high quantum yield of [Cr(ddpd)₂]³⁺ enables optical pressure sensing in aqueous and methanolic solution. These unique features of the molecular rubies [Cr(ddpd)₂]³⁺ and [Cr(H₂tpda)₂]³⁺ pave the way for highly sensitive optical pressure determination and unprecedented molecule‐based pressure sensing with a single type of emitter.     

Charge-Transfer and Spin-Flip States: Thriving as Complements

Transition metal complexes with photoactive charge-transfer excited states are pervasive throughout the literature. In particular, [Ru(bpy)₃]²⁺ (bpy=2,2′-bipyridine), with its metal-to-ligand charge-transfer emission, has been established as a key complex. Meanwhile, interest in so-called spin-flip metal-centered states has risen dramatically after the molecular ruby [Cr(ddpd)₂]³⁺ (ddpd=N,N′-dimethyl-N,N′-dipyridin-2-yl-pyridine-2,6-diamine) led to design principles to access strong, long-lived emission from photostable chromium(III) complexes. This Review contrasts the properties of emissive charge-transfer and spin-flip states by using [Ru(bpy)₃]²⁺ and [Cr(ddpd)₂]³⁺ as prototypical examples. We discuss the relevant excited states, the tunability of their energy and lifetimes, and their response to external stimuli. Finally, we identify strengths and weaknesses of charge-transfer and spin-flip states in applications such as photocatalysis and circularly polarized luminescence.     

Ligand‐Centred Reactivity of Bis(picolyl)amine Iridium: Sequential Deprotonation,Oxidation and Oxygenation of a “Non‐Innocent” Ligand

Treatment of [Ir(bpa)(cod)]⁺ complex [ 1 ]⁺ with a strong base (e.g., tBuO^?) led to unexpected double deprotonation to form the anionic [Ir(bpa?2H)(cod)]^? species [ 3 ]^?, via the mono‐deprotonated neutral amido complex [Ir(bpa?H)(cod)] as an isolable intermediate. A certain degree of aromaticity of the obtained metal–chelate ring may explain the favourable double deprotonation. The rhodium analogue [ 4 ]^? was prepared in situ. The new species [M(bpa?2H)(cod)]^? (M=Rh, Ir) are best described as two‐electron reduced analogues of the cationic imine complexes [M^I(cod)(Py‐CH₂‐N?CH‐Py)]⁺. One‐electron oxidation of [ 3 ]^? and [ 4 ]^? produced the ligand radical complexes [ 3 ]^. and [ 4 ]^.. Oxygenation of [ 3 ]^? with O₂ gave the neutral carboxamido complex [Ir(cod)(py‐CH₂‐N‐CO‐py)] via the ligand radical complex [ 3 ]^. as a detectable intermediate.     

A Heteroleptic Push–Pull Substituted Iron(II) Bis(tridentate) Complex with Low‐Energy Charge‐Transfer States

A heteroleptic iron(II) complex [Fe(dcpp)(ddpd)]²⁺ with a strongly electron‐withdrawing ligand (dcpp, 2,6‐bis(2‐carboxypyridyl)pyridine) and a strongly electron‐donating tridentate tripyridine ligand (ddpd, N,N′‐dimethyl‐N,N′‐dipyridine‐2‐yl‐pyridine‐2,6‐diamine) is reported. Both ligands form six‐membered chelate rings with the iron center, inducing a strong ligand field. This results in a high‐energy, high‐spin state (⁵T₂, (t_2g)⁴(e_g*)²) and a low‐spin ground state (¹A₁, (t_2g)⁶(e_g*)⁰). The intermediate triplet spin state (³T₁, (t_2g)⁵(e_g*)¹) is suggested to be between these states on the basis of the rapid dynamics after photoexcitation. The low‐energy π^* orbitals of dcpp allow low‐energy MLCT absorption plus additional low‐energy LL′CT absorptions from ddpd to dcpp. The directional charge‐transfer character is probed by electrochemical and optical analyses, Mößbauer spectroscopy, and EPR spectroscopy of the adjacent redox states [Fe(dcpp)(ddpd)]³⁺ and [Fe(dcpp)(ddpd)]⁺, augmented by density functional calculations. The combined effect of push–pull substitution and the strong ligand field paves the way for long‐lived charge‐transfer states in iron(II) complexes.     

Three structures of dispirooxindole derivatives generated in situ through a three‐component one‐pot strategy with complete regio‐ and stereoselectivity

The challenging molecular architecture of spirooxindoles is appealing to chemists because it evokes novel synthetic strategies that address configurational demands and provides platforms for further reaction development. The [3+2] cycloaddition of the carbonyl ylide with arylideneoxindole via a five‐membered cyclic transition state gave a novel class of dispirooxindole derivatives, namely tert‐butyl 4′‐(4‐bromophenyl)‐1′′‐methyl‐2,2′′‐dioxo‐5′‐phenyl‐4′,5′‐dihydrodispiro[indoline‐3,2′‐furan‐3′,3′′‐indoline]‐1‐carboxylate, C₃₆H₃₁BrN₂O, (Ia), 5′‐(4‐bromophenyl)‐1,1′′‐dimethyl‐4′‐phenyl‐4′,5′‐dihydrodispiro[indoline‐3,2′‐furan‐3′,3′′‐indoline]‐2,2′′‐dione, C₃₂H₂₅BrN₂O₃, (Ib), and tert‐butyl 1′′‐methyl‐2,2′′‐dioxo‐4′‐phenyl‐5′‐(p‐tolyl)‐4′,5′‐dihydrodispiro[indoline‐3,2′‐furan‐3′,3′′‐indoline]‐1‐carboxylate, C₃₇H₃₄N₂O₅, (Ic). Crystal structure analyses of these dispirooxindoles revealed the formation of two diastereoisomers selectively and confirmed their relative stereochemistry (SSSR and RRRS). In all three structures, intramolecular C—H...O and π–π interactions between oxindole and dihydrofuran rings are the key factors governing the regio‐ and stereoselectivity, and in the absence of conventional hydrogen bonds, their crystal packings are strengthened by intermolecular C—H...π interactions.     

Darstellung und Kristallstruktur des Lithium‐Strontium‐Hydridnitrids LiSr2H2N

Synthesis and Crystal Structure of the Lithium Strontium Hydride Nitride LiSr₂H₂N LiSr₂H₂N was synthesized by the reaction of LiH and Li₃N with elemental strontium in sealed tantalum tubes at 650 °C within seven days. This second example of a quaternary hydride nitride crystallizes orthorhombically in space group Pnma (no. 62) with the lattice constants a = 747.14(5) pm, b = 370.28(3) pm and c = 1329.86(9) pm (Z = 4). Its crystal structure contains both kinds of anions H^? and N^3? in a sixfold distorted octahedral metal cation coordination each. The coordination polyhedra [(H1)Sr₅Li]¹⁰⁺, trans‐[(H2)Sr₄Li₂]⁹⁺ and [NSr₅Li]⁸⁺ are connected via edges and corners to form a three‐dimensional network. Two crystallographically different Sr²⁺ cations exhibit a sevenfold monocapped trigonal prismatic coordination by H^? and N^3? with [(Sr1)H₅N₂]^9? and [(Sr2)H₄N₃]^11? polyhedra, wheras Li⁺ shows a nearly planar fourfold coordinative environment ([LiH₃N]^5?). Cationic double chains of edge‐shared [NSr₅Li]⁸⁺ octahedra dominate the structure according to . Running parallel to the [0 1 0] direction, they are bundled like a hexagonal rod‐packing which is interconnected by H^? anions within the (0 0 1) plane first and finally even in the third dimension (i. e. along [0 0 1]). Therefore the structure of LiSr₂H₂N is compared to that one of the closely related quaternary hydride oxide LiLa₂HO₃.     

A Stable Crystalline Copper(I)–N2O Complex Stabilized as the Salt of a Weakly Coordinating Anion

Nitrous oxide is considered a poor ligand, and therefore only a handful of well‐defined metal–N₂O complexes are known. Oxidation of copper powder with an extreme oxidant, [Ag₂I₂][ An ]₂ ([ An ]^?=[Al(OC(CF₃)₃)₄]^?) in perfluorinated hexane leads to Cu^I[ An ], the first auxiliary ligand‐free Cu^I salt of the perfluorinated alkoxyaluminate anion. The compound is capable of forming a stable and crystalline complex with nitrous oxide, Cu(N₂O)[ An ], where the Cu?N₂O bond is by far the strongest among all other molecular metal–N₂O complexes known. Thorough characterization of the compounds together with the crystal structure of Cu(N₂O)[ An ] complex supported with DFT calculations are presented. These give insight into the bonding in the Cu⁺–N₂O system and confirm N‐end coordination of the ligand.     

Polymerization of acrylamide with persulfate–thiomalic acid initiator

The redox system of potassium persulfate–thiomalic acid (I₁–I₂) was used to initiate the polymerization of acrylamide (M) in aqueous medium. For 20–30% conversion the rate equation is where R_p is the rate of polymerization. Activation energy is 8.34 kcal deg^?1 mole^?1 in the investigated range of temperature 25–45°C. M_n is directly proportional to [M] and inversely to [I₁]. The range of concentrations for which these observations hold at 35°C and pH 4.2 are [I₁] = (1.0–3.0) × 10^?3, [I₂] = (3.0–7.5) × 10^?3, and [M] = 5.0 × 10^?2–3.0 × 10^?1 mole/liter.     

Electroanalytical Studies of Chromone Based Ionophores for the Selective Determination of Arsenite Ion

Two chemosensors 4H‐1‐benzopyran‐3‐carboxaldehyde, 4‐oxo‐, 3‐(2‐phenylhydrazone), [I₁] and 4H‐1‐benzopyran‐3‐carboxaldehyde, 4‐oxo‐, 3‐[2‐(2,4‐dinitrophenyl)hydrazone], [I₂] with hydrazone‐NH group as binding site have been shown excellent selectivity for arsenite ion. It is confirmed by the UV‐vis titration that I₂ is more selective than I₁. The performance of the coated graphite electrode (CGE) was found to be better than polymeric membrane electrode (PME) in terms of linear range of 4.89×10^?7–1.0×10^?1 mol L^?1, low detection limit of 8.31×10^?8 mol L^?1 and short response time. The proposed sensors were also used to determine the arsenite ion in different water samples.     

Experimental and Computational Studies of a Multi‐Electron Donor–Acceptor Ligand Containing the Thiazolo[5,4‐d]thiazole Core and its Incorporation into a Metal–Organic Framework

A ligand containing the thiazolo[5,4‐d]thiazole (TzTz) core (acceptor) with terminal triarylamine moieties (donors), N,N′‐(thiazolo[5,4‐d]thiazole‐2,5‐diylbis(4,1‐phenylene))bis(N‐(pyridine‐4‐yl)pyridin‐4‐amine ( 1 ), was designed as a donor–acceptor system for incorporation into electronically active metal–organic frameworks (MOFs). The capacity for the ligand to undergo multiple sequential oxidation and reduction processes was examined using UV/Vis‐near‐infrared spectroelectrochemistry (UV/Vis‐NIR SEC) in combination with DFT calculations. The delocalized nature of the highest occupied molecular orbital (HOMO) was found to inhibit charge‐transfer interactions between the terminal triarylamine moieties upon oxidation, whereas radical species localized on the TzTz core were formed upon reduction. Conversion of 1 to diamagnetic 2+ and 4+ species resulted in marked changes in the emission spectra. Incorporation of this highly delocalized multi‐electron donor–acceptor ligand into a new two‐dimensional MOF, [Zn(NO₃)₂( 1 )] ( 2 ), resulted in an inhibition of the oxidation processes, but retention of the reduction capability of 1 . Changes in the electrochemistry of 1 upon integration into 2 are broadly consistent with the geometric and electronic constraints enforced by ligation.     

Metal‐Mediated [2+3] Cycloaddition of Nitrones to Palladium‐Bound Isonitriles

[2+3] Cycloadditions! The metal‐mediated [2+3] cycloaddition of acyclic [^?O⁺N(R²)?(H)R³] and nonaromatic cyclic nitrones [^?O⁺N^a?CHCH₂CH₂C^bMe₂(N^a? C^b)] to palladium‐bound isonitriles cis‐[PdCl₂(C?NR)₂] proceeds under mild conditions to furnish novel heterocyclic carbene complexes, which then undergo N? O bond rupture to give imino complexes and free isocyanates (see scheme).

     

Rearrangements in Model Peptide‐Type Radicals via Intramolecular Hydrogen‐Atom Transfer

Intramolecular H‐atom transfer in model peptide‐type radicals was investigated with high‐level quantum‐chemistry calculations. Examination of 1,2‐, 1,3‐, 1,5‐, and 1,6[C ? N]‐H shifts, 1,4‐ and 1,7[C ? C]‐H shifts, and 1,4[N ? N]‐H shifts (Scheme 1), was carried out with a number of theoretical methods. In the first place, the performance of UB3‐LYP (with the 6‐31G(d), 6‐31G(2df,p), and 6‐311+G(d,p) basis sets) and UMP2 (with the 6‐31G(d) basis set) was assessed for the determination of radical geometries. We found that there is only a small basis‐set dependence for the UB3‐LYP structures, and geometries optimized with UB3‐LYP/6‐31G(d) are generally sufficient for use in conjunction with high‐level composite methods in the determination of improved H‐transfer thermochemistry. Methods assessed in this regard include the high‐level composite methods, G3(MP2)‐RAD, CBS‐QB3, and G3//B3‐LYP, as well as the density‐functional methods B3‐LYP, MPWB1K, and BMK in association with the 6‐31+G(d,p) and 6‐311++G(3df,3pd) basis sets. The high‐level methods give results that are close to one another, while the recently developed functionals MPWB1K and BMK provide cost‐effective alternatives. For the systems considered, the transformation of an N‐centered radical to a C‐centered radical is always exothermic (by 25 kJ ? mol^?1 or more), and this can lead to quite modest barrier heights of less than 60 kJ ? mol^?1 (specifically for 1,5[C ? N]‐H and 1,6[C ? N]‐H shifts). H‐Migration barriers appear to decrease as the ring size in the transition structure (TS) increases, with a lowering of the barrier being found, for example when moving from a rearrangement proceeding via a four‐membered‐ring TS (e.g., the 1,3[C ? N]‐H shift, CH₃? C(O)? NH^. → ^.CH₂? C(O)? NH₂) to a rearrangement proceeding via a six‐membered‐ring TS (e.g., the 1,5[C ? N]‐H shift, ^.NH? CH₂? C(O)? NH? CH₃ → NH₂? CH₂? C(O)? NH? CH₂^.).     

Hydrogels Composed of Organic Amphiphiles and α‐Cyclodextrin: Supramolecular Networks of Their Pseudorotaxanes in Aqueous Media

Mixtures of N‐alkyl pyridinium compounds [py‐N‐(CH₂)_nOC₆H₃‐3,5‐(OMe)₂]⁺(X^?) ( 1b Cl: n=10, X=Cl; 1c Br: n=12, X=Br) and α‐cyclodextrin (α‐CD) form supramolecular hydrogels in aqueous media. The concentrations of the two components influences the sol–gel transition temperature, which ranges from 7 to 67 °C. Washing the hydrogel with acetone or evaporation of water left the xerogel, and ¹³C CP/MAS NMR measurements, powder X‐ray diffraction (XRD), and scanning electron microscopy (SEM) revealed that the xerogel of 1b Cl (or 1c Br) and α‐CD was composed of pseudorotaxanes with high crystallinity. ¹³C{¹H} and ¹H NMR spectra of the gel revealed the detailed composition of the components. The gel from 1b Cl and α‐CD contains the corresponding [2]‐ and [3]pseudorotaxanes, [ 1b? (α‐CD)]Br and [ 1b? (α‐CD)₂]Br, while that from 1c Br and α‐CD consists mainly of [3]pseudorotaxane [ 1c? (α‐CD)₂]Br. 2D ROESY ¹H NMR measurements suggested intermolecular contact of 3,5‐dimethoxyphenyl and pyridyl end groups of the axle component. The presence of the [3]pseudorotaxane is indispensable for gel formation. Thus, intermolecular interaction between the end groups of the axle component and that between α‐CDs of the [3]pseudorotaxane contribute to formation of the network. The supramolecular gels were transformed into sols by adding denaturing agents such as urea, C₆H₃‐1,3,5‐(OH)₃, and [py‐N‐nBu]⁺(Cl^?).     

Two hydro­chlorides of 7‐methyl‐3,7,11,17‐tetra­aza­bi­cyclo­[11.3.1]­heptadeca‐1(17),13,15‐triene

The X‐ray structure determinations of the two title com­pounds, namely 7‐methyl‐7,17‐di­aza‐3,11‐diazo­niabi­cyclo[11.3.1]­hep­ta­deca‐1(17),13,15‐triene dichloride monohydrate, C₁₄H₂₆N₄²⁺·2Cl^?·H₂O, (I), and 7‐methyl‐17‐aza‐3,7,11‐triazo­niabi­cyclo­[11.3.1]­heptadeca‐1(17),13,15‐triene 2.826‐chloride 0.174‐nitrate, C₁₄H₂₇N₄³⁺·2.826Cl^?·0.174NO₃^?, (II), are re­ported. Protonation occurs at the secondary amine N atoms in (I) and at all three amine N atoms in (II) to which the Cl^? ions are linked via N—H?Cl hydrogen bonds. The macrocyclic hole is quite different in both structures, as is observed by comparing particularly the N3?N4 distances [2.976 (4) and 4.175 (4) Å for (I) and (II), respectively]. In (II), a Cl^? ion alternates with an NO₃^? ion in a disordered structure.     

Coordination Behavior of a D‐Penicillaminato Aurate(I) Metalloligand Toward Coblat(III) Centers

Treatment of (NH₄)[Au(D‐Hpen‐S)₂](D‐H₂pen = D‐penicillamine) with CoCl₂·6H₂O in an acetate buffer solution, followed by air oxidation, gave neutral Au^ICo^III and anionic Au^I₃Co^III₂ polynuclear complexes, [Au₃Co₃(D‐pen‐N,O,S)₆]([ 1 ]) and [Au₃Co₂(D‐pen‐N,S)₆]^3? ([ 2 ]^3?), which were separated by anion‐exchange column chromatography. Complexes [ 1 ] and [ 2 ]^3? each formed a single isomer, and their structures were determined by single‐crystal X‐ray crystallography. In [ 1 ], each of three [Au(D‐pen‐S)₂]^3?metalloligands coordinates to two Co^III ions in a bis‐tridentate‐N,O,S mode to form a cyclic Au^I₃Co^III₃ hexanuclear structure, in which three [Co(D‐pen‐N,O,S)₂]^? octahedral units and six bridging S atoms adopt trans(O) geometrical and R chiral configurations, respectively. In [ 2 ]^3?, each of three [Au(D‐pen‐S)₂]^3? metalloligands coordinates to two Co^III ions in a bis‐bidentate‐N,S mode to form a Au^I₃Co^III₂ pentanuclear structure, in which two [Co(D‐pen‐N,S)₃]^3? units and six bridging S atoms adopt ∧ and R chiral configurations, respectively.     

Selective Determination of Zn2+ Ion in Various Environmental,Biological and Medicinal Plant Samples Using a Novel Coated Graphite Electrode

Novel Zn²⁺ ion‐selective PVC based coated graphite electrodes were fabricated using the ionophores N‐((1H‐indol‐3‐yl)methylene)thiazol‐2‐amine (I₁), N‐((1H‐indol‐3‐yl)methyl)‐thiazol‐2‐amine (I₂) and 1‐((1H‐indol‐3‐yl)methylene)urea (I₃). Their potentiometric performance was examined in dependence of the addition of plasticizers and anion excluders and compared. It is found that the coated graphite electrode with the composition I₁:KTpClPB:o‐NPOE:PVC=9 : 1.5 : 51 : 38.5 is the best with respect to the wide working concentration range (4.2×10^?8–1.0×10^?1 mol L^?1), low detection limit (1.6×10^?8 mol L^?1) and wide pH range of 3.0–8.0. The proposed electrode was successfully applied to quantify Zn²⁺ in various environmental, biological and medicinal plant samples and used as indicator electrode.     

Voltammetry of Dissolved Iron(III)–Nitrilotriacetate–Hydroxide System in Water Solution

The investigation of the dissolved iron(III)–nitrilotriacetate–hydroxide system in the water solution (I=0.1 mol L^?1 in NaClO₄; pH 8.0±0.1) using differential pulse cathodic voltammetry, cyclic voltammetry, and sampled direct current (DC) polarography, was carried out on a static mercury drop electrode (SMDE). The dissolved iron(III) ion concentrations varied from 2.68×10^?6 to 6×10^?4 mol L^?1 and nitrilotriacetate concentrations were 1×10^?4 and 5×10^?4 mol L^?1. By deconvoluting of the overlapped reduction voltammetric peaks using Fourier transformation, four relatively stable, dissolved iron(III) complex species were characterized, as follows: [Fe(NTA)₂]^3?, mixed ligand complexes [FeOHNTA]^? and [Fe(OH)₂NTA]^2?, showing a one‐electron quasireversible reduction, and binuclear diiron(III) complex [NTAFeOFeNTA]^2?, detected above 4×10^?4 mol L^?1 of the added iron(III) ions, showing a one‐electron irreversible reduction character. The calculations with the constants from the literature were done and compared with the potential shifts of the voltammetric peaks. Fitting was obtained by changing the following literature constants: log β₂([Fe(NTA)₂]^3?) from 24 to 27.2, log β₁([FeNTA]^?) from 8.9 to 9.2, log β₂([Fe(NTA)₂]^4?) from 11.89 to 15.7 and log β₂([Fe(OH)₂NTA]^3?) from 15.63 to 19. The determination of the electrochemical parameters of the mixed ligand complex [FeOHNTA]^?, such as: transfer coefficient (α), rate constant (k_s) and formal potential (E°') was done using a sampled DC polarography, and found to be 0.46±0.05, 1.0±0.3×10^?3 cm s^?1, and ?0.154±0.010 V, respectively. Although known previously in the literature, these four species have now for the first time been recorded simultaneously, i.e. proved to exist simultaneously under the given conditions.     

Synthesis of N,N,N-4,4＂-Di-（4-methylphenyl）-2,2＇：6＇,2＂- terpyridine-N,N,N-tris（isothiocyanato） Ruthenium（Ⅱ） and Application to Colorimetric Hg^2＋ Sensor

A terpyridine derivative DPTP [di-（4-methylphenyl）-2,2＇：6＇,2＂-terpyridine] was conveniently synthesized from 2-bromopyridine via halogen-dance reaction, Kharash coupling and Stille coupling reaction. Then its corresponding ruthenium complex Ru-DPTP [N,N,N-4,4＇＇-di-（4-methy,phenyl）-2,2＇：6＇,2＂-terpyridine-N,N,N-tris（is,-thi,cyanat,）- ruthenium（H） ammonium] was obtained and fully characterized by IR, UV-Vis, ESI MS and elemental analysis. The MLCT absorption band of Ru-DPTP was blue-shifted from 570 to 500 nm upon addition of Hg^2＋. Among a series of surveyed metal ions, the complex showed a unique recognition to Hg^2＋, indicating that it can be used as a selective colorimetric sensor for Hg^2＋.