Phenylacetylide Complex Research Articles

Synthesis, Photoluminescence, and Electroluminescence of Phosphorescent Dipyrido[3,2-a;2'3'-c]phenazine-Platinum(II) Complexes Bearing Hole-Transporting Acetylide Ligands.

In this study, novel phosphorescent dipyrido[3,2-a;2'3'-c]phenazine (dppz)-platinum(II)-phenylacetylide complexes were developed to fabricate non-doped organic light-emitting diodes (OLED) by solution-processing. To facilitate the charge carrier injection into the emitting layer (EML), 3,6-di-tert-butylcarbazole-functinalized phenylacetylides were employed. As for the dppz ligand, 9,9-dihexylfluoren-2-yl and 4-hexylthiophen-2-yl side-arms were introduced to the 2,7-positions, which led to reddish orange and red photoluminescence (PL), respectively, in solution and film states (PL wavelength: ca. 600 and ca. 625 nm, respectively). The carbazole-appended phenylacetylide ligands hardly affected the emission color, although unsubstituted phenylacetylides gave rise to aggregate- or excimer-based near-infrared PL with a low quantum yield. Two types of non-doped OLEDs were fabricated: single-layer and multilayer devices. In both devices, the organic layers were fabricated by spin-coating, and the EML consisted of a neat film of the corresponding platinum(II) complex. Therein, electroluminescence spectra corresponding to those of PL were observed. The single-layer devices exhibited low device efficiencies due to a deteriorated charge carrier balance. The multilayer devices possessed hole- and electron-transporting layers on the anode and cathode sides of the EML, respectively. Owing to an improved charge carrier balance, the multilayer devices exhibited higher device performance, affording considerably improved values of luminance and external quantum efficiency.

Platinum(II)-Substituted Phenylacetylide Complexes Supported by Acyclic Diaminocarbene Ligands.

We introduce phosphorescent platinum aryl acetylide complexes supported by tert-butyl-isocyanide and strongly σ-donating acyclic diaminocarbene (ADC) ligands. The precursor complexes cis-[Pt(CNtBu)2(C≡CAr)2] (4a-4f) are treated with diethylamine, which undergoes nucleophilic addition with one of the isocyanides to form the cis-[Pt(CNtBu)(ADC)(C≡CAr)2] complexes (5a-5f). The new compounds incorporate either electron-donating groups (4-OMe and 4-NMe2) or electron-withdrawing groups [3,5-(OMe)2, 3,5-(CF3)2, 4-CN, and 4-NO2] on the aryl acetylide. Experimental HOMO-LUMO gaps, estimated from cyclic voltammetry, span the range of 2.68-3.61 eV and are in most cases smaller than the unsubstituted parent complex, as corroborated by DFT. In the ADC complexes, peak photoluminescence wavelengths span the range of 428 nm (2a, unsubstituted phenylacetylide) to 525 nm (5f, 4-NO2-substituted), with the substituents inducing a red shift in all cases. The phosphorescence E0,0 values and electrochemical HOMO-LUMO gaps are loosely correlated, showing that both can be reduced by either electron-donating or electron-withdrawing substituents on the aryl acetylides. The photoluminescence quantum yields in the ADC complexes are between 0.044 and 0.31 and the lifetimes are between 4.8 and 14 μs, a factor of 1.8-10× higher (for ΦPL) and 1.2-3.6× longer (for τ) than the respective isocyanide precursor (ΦPL = 0.014-0.12, τ = 2.8-8.2 μs).

Bioorthogonal Activation of Dual Catalytic and Anti‐Cancer Activities of Organogold(I) Complexes in Living Systems

AbstractControllably activating the bio‐reactivity of metal complexes in living systems is challenging but highly desirable because it can minimize off‐target bindings and improve spatiotemporal specificity. Herein, we report a new bioorthogonal activation approach by employing Pd(II)‐triggered transmetallation reactions to conditionally activate the bio‐reactivity of NHC–Au(I)–phenylacetylide complexes (1 a) in vitro and in vivo. A combination of1H NMR, LC‐MS, DFT calculation and fluorescence screening assays reveals that1 adisplays a reasonable stability against biological thiols, but its phenylacetylide ligand can be efficiently transferred to Pd(II), leading to in situ formation of labile NHC–Au(I) species that is catalytically active inside living cells and zebrafish, and can meanwhile effectively suppress the activity of thioredoxin reductase, potently inhibit the proliferation of cancer cells and efficiently suppress angiogenesis in zebrafish models.

Bioorthogonal Activation of Dual Catalytic and Anti-Cancer Activities of Organogold(I) Complexes in Living Systems.

Controllably activating the bio-reactivity of metal complexes in living systems is challenging but highly desirable because it can minimize off-target bindings and improve spatiotemporal specificity. Herein, we report a new bioorthogonal activation approach by employing Pd(II)-triggered transmetallation reactions to conditionally activate the bio-reactivity of NHC-Au(I)-phenylacetylide complexes (1 a) in vitro and in vivo. A combination of 1 H NMR, LC-MS, DFT calculation and fluorescence screening assays reveals that 1 a displays a reasonable stability against biological thiols, but its phenylacetylide ligand can be efficiently transferred to Pd(II), leading to in situ formation of labile NHC-Au(I) species that is catalytically active inside living cells and zebrafish, and can meanwhile effectively suppress the activity of thioredoxin reductase, potently inhibit the proliferation of cancer cells and efficiently suppress angiogenesis in zebrafish models.

Tris(dicyclohexylamido) Group 4 Metal Allyl and Phenylacetylide Complexes – Synthesis and Characterization

The synthesis and characterization of organyl complexes derived from group 4 metal dicyclohexylamido complexes (Cy2N)3MCl (Cy: Cyclohexyl, M = Ti, Zr, Hf 1‐M) is presented. The allyl Grignard reagent is used to obtain the corresponding group 4 allyl complexes 2‐M, and lithium phenylacetylide is used to obtain the phenylacetylide complexes 3‐M. The thermal stability of complexes 2‐M and 3‐M is investigated. All complexes are characterized by NMR spectroscopy and single‐crystal X‐ray diffraction. Their molecular structures in solution and in the solid state are discussed.

Further Evidence for 'Extended' Cumulene Complexes: Derivatives from Reactions with Halide Anions and Water.

Reactions of [Ru{C=C(H)-1,4-C6 H4 C≡CH}(PPh3 )2 Cp]BF4 ([1 a]BF4 ) with hydrohalic acids, HX, results in the formation of [Ru{C≡C-1,4-C6 H4 -C(X)=CH2 }(PPh3 )2 Cp] [X=Cl (2 a-Cl), Br (2 a-Br)], arising from facile Markovnikov addition of halide anions to the putative quinoidal cumulene cation [Ru(=C=C=C6 H4 =C=CH2 )(PPh3 )2 Cp]+ . Similarly, [M{C=C(H)-1,4-C6 H4 -C≡CH}(LL)Cp ]BF4 [M(LL)Cp'=Ru(PPh3 )2 Cp ([1 a]BF4 ); Ru(dppe)Cp* ([1 b]BF4 ); Fe(dppe)Cp ([1 c]BF4 ); Fe(dppe)Cp* ([1 d]BF4 )] react with H+ /H2 O to give the acyl-functionalised phenylacetylide complexes [M{C≡C-1,4-C6 H4 -C(=O)CH3 }(LL)Cp'] (3 a-d) after workup. The Markovnikov addition of the nucleophile to the remote alkyne in the cations [1 a-d]+ is difficult to rationalise from the vinylidene form of the precursor and is much more satisfactorily explained from initial isomerisation to the quinoidal cumulene complexes [M(=C=C=C6 H4 =C=CH2 )(LL)Cp']+ prior to attack at the more exposed, remote quaternary carbon. Thus, whilst representative acetylide complexes [Ru(C≡C-1,4-C6 H4 -C≡CH)(PPh3 )2 Cp] (4 a) and [Ru(C≡C-1,4-C6 H4 -C≡CH)(dppe)Cp*] (4 b) reacted with the relatively small electrophiles [CN]+ and [C7 H7 ]+ at the β-carbon to give the expected vinylidene complexes, the bulky trityl ([CPh3 ]+ ) electrophile reacted with [M(C≡C-1,4-C6 H4 -C≡CH)(LL)Cp'] [M(LL)Cp'=Ru(PPh3 )2 Cp (4 a); Ru(dppe)Cp* (4 b); Fe(dppe)Cp (4 c); Fe(dppe)Cp* (4 d)] at the more exposed remote end of the carbon-rich ligand to give the putative quinoidal cumulene complexes [M{C=C=C6 H4 =C=C(H)CPh3 }(LL)Cp']+ , which were isolated as the water adducts [M{C≡C-1,4-C6 H4 -C(=O)CH2 CPh3 }(LL)Cp'] (6 a-d). Evincing the scope of the formation of such extended cumulenes from ethynyl-substituted arylvinylene precursors, the rather reactive half-sandwich (5-ethynyl-2-thienyl)vinylidene complexes [M{C=C(H)-2,5-c C4 H2 S-C≡CH}(LL)Cp']BF4 ([7 a-d]BF4 add water readily to give [M{C≡C-2,5-c C4 H2 S-C(=O)CH3 }(LL)Cp'] (8 a-d)].

Co(III) phenylacetylide complexes supported by tetraazamacrocyclic ligands: Syntheses and characterizations

Reported herein are the syntheses and characterization of mono- and bis- Co(III) phenylacetylide complexes trans-[Co(L)(C2Ph)Cl]+ (2a/b) and trans-[Co(L)(C2Ph)2]+ (3a/b), where L is MPD (a) or MPC (b) (MPD = 5,12-dimethyl-7,14-diphenyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene, MPC = 5,12-dimethyl-9,14-diphenyl-1,4,8,11-tetraazacyclotetradecane). All the new complexes were characterized by UV–Vis, FT-IR spectroscopic and voltammetric techniques. Single crystal X-ray diffraction studies revealed that the MPD ligand is a stronger donor to the Co(III) center than the MPC ligand, and the enhanced CoN interactions manifest some subtle contrast in terms of spectroscopic and voltammetric properties between Co(MPD) and Co(MPC) complexes. These experimental observations were further corroborated by DFT calculations.

Glucose-Appended Platinum(II)-BODIPY Conjugates for Targeted Photodynamic Therapy in Red Light.

Platinum(II) complexes [Pt(L1)(R-BODIPY)]Cl (1) and [Pt(L2)(R-BODIPY)]Cl (2), where R-BODIPY is 8-(4-ethynylphenyl)-distyryl-4,4-difluoro-5,7-dimethyl-4-bora-3a,4a-diaza-s-indacene-3, L1 is 4'-phenyl-2,2':6',2″-terpyridine, and L2 is (2,2':6',2″-terpyridin-4'-oxy)ethyl-β-d-glucopyranoside, were synthesized and characterized, and their photocytotoxicity was studied. The phenylacetylide complex [Pt(L1)(C≡CPh)]Cl (3) was prepared and used as a control. Complexes 1 and 2 showed near-IR absorption bands at 713 nm (ε = 3.47 × 104 M-1 cm-1) and 715 nm (3.2 × 104 M-1 cm-1) in 10% dimethyl sulfoxide (DMSO)-Dulbecco's Modified Eagle's Medium (DMEM) (pH 7.2). The BODIPY complexes are emissive in 10% DMSO-DMEM at pH 7.2 with λem (λex, Φf) = 822 nm (710 nm, 0.022) for complex 1 and λem (λex, Φf) = 825 nm (710 nm, 0.026) for complex 2. They generated singlet oxygen (1O2) in red light as evidenced from 1,3-diphenylisobenzofuran (DPBF) titration experiments. The singlet oxygen quantum yield (ΦΔ) values for 1 and 2 were ∼0.6 signifying their photosensitizing ability. They were remarkably photodynamic therapy (PDT) active in red light showing significant red light-induced cytotoxicity in cervical HeLa, lung cancer A549, and breast cancer MCF-7 cells (IC50: 2.3-24.7 μM in light) with negligible dark toxicity (IC50 > 100 μM). A significant enhancement in cellular uptake was observed for 2 having glucose-appended terpyridine ligand compared to 1. The confocal microscopy showed significant mitochondrial localization of the complexes as evidenced from the JC-1 assay. The complexes released the photoactive R-BODIPY ligand upon red light-irradiation as evidenced from the mass and 1H NMR spectral studies. Complex 2 is remarkable in satisfying the essential requirements of targeted PDT in red light.

Highly Fluorinated Tris(indazolyl)borate Hydrocarbyl Complexes of Calcium and Magnesium: Synthesis and Structural Studies

Heteroleptic phenylacetylide complexes [{F12-Tp4Bo,3Ph}Ae(C≡CPh)]x of calcium (Ae = Ca, x = 2; 2) and magnesium (Ae = Mg, x = 1; 4) containing the highly fluorinated 3-phenyl hydrotris(indazolyl)borate {F12-Tp4Bo,3Ph}− ligand have been synthesized by acid–base reactions between the corresponding silylamido derivatives [{F12-Tp4Bo,3Ph}Ae{N(SiRMe2)2}] (R = Me, Ae = Ca (1); R = H, Ae = Mg (3)) and PhC≡CH. Compounds 2 and 4 have been characterized by NMR spectroscopy and X-ray diffraction analysis. 2 crystallizes as a dinuclear complex, showing two nonsymmetrical “side-on” (π-type) interactions between the acetylide units and the Ca centers, whereas 4 crystallizes as a mononuclear complex, displaying a four-coordinate magnesium. The molecular structure of the complex [{F12-Tp4Bo,3Ph}Mg{N(SiMe2H)2}] (3), obtained by the salt metathesis reaction between [Mg{N(SiMe2H)2}2] and [Tl{F12-Tp4Bo,3Ph}], is also reported. 3 is also four-coordinate and exhibits a Mg···β-Si–H agostic distortion. The synthesis and in situ characterization of the heteroleptic alkyl complex [{F12-Tp4Bo,3Ph}Ca{CH(SiMe3)2}(THF)] (5) is also reported, although attempts to isolate this compound failed due to its extreme sensitivity to temperature.

Well‐Defined Dinuclear Gold Complexes for Preorganization‐Induced Selective Dual Gold Catalysis

The synthesis, reactivity, and potential of well-defined dinuclear gold complexes as precursors for dual gold catalysis are explored. Using the preorganizing abilities of the ditopic PN(H) P(iPr) (L(H) ) ligand, dinuclear Au(I) -Au(I) complex 1 and mixed-valent Au(I) -Au(III) complex 2 provide access to structurally characterized chlorido-bridged cationic species 3 and 4 upon halide abstraction. For 2, this transformation involves unprecedented two-electron oxidation of the redox-active ligand, generating a highly rigidified environment for the Au2 core. Facile reaction with phenylacetylene affords the σ,π-activated phenylacetylide complex 5. When applied in the dual gold heterocycloaddition of a urea-functionalized alkyne, well-defined precatalyst 3 provides high regioselectivities for the anti-Markovnikov product, even at low catalyst loadings, and outperforms common mononuclear Au(I) systems. This proof-of-concept demonstrates the benefit of preorganization of two gold centers to enforce selective non-classical σ,π-activation with bifunctional substrates.

Well‐Defined Dinuclear Gold Complexes for Preorganization‐Induced Selective Dual Gold Catalysis

AbstractThe synthesis, reactivity, and potential of well‐defined dinuclear gold complexes as precursors for dual gold catalysis are explored. Using the preorganizing abilities of the ditopic PNHPiPr (LH) ligand, dinuclear AuI–AuI complex 1 and mixed‐valent AuI–AuIII complex 2 provide access to structurally characterized chlorido‐bridged cationic species 3 and 4 upon halide abstraction. For 2, this transformation involves unprecedented two‐electron oxidation of the redox‐active ligand, generating a highly rigidified environment for the Au2 core. Facile reaction with phenylacetylene affords the σ,π‐activated phenylacetylide complex 5. When applied in the dual gold heterocycloaddition of a urea‐functionalized alkyne, well‐defined precatalyst 3 provides high regioselectivities for the anti‐Markovnikov product, even at low catalyst loadings, and outperforms common mononuclear AuI systems. This proof‐of‐concept demonstrates the benefit of preorganization of two gold centers to enforce selective non‐classical σ,π‐activation with bifunctional substrates.

Pt(II) and Pt(IV) Amido, Aryloxide, and Hydrocarbyl Complexes: Synthesis, Characterization, and Reaction with Dihydrogen and Substrates that Possess C−H Bonds

The Pt(II) amido and phenoxide complexes ((t)bpy)Pt(Me)(X), ((t)bpy)Pt(X)(2), and [((t)bpy)Pt(X)(py)][BAr'(4)] (X = NHPh, OPh; py = pyridine) have been synthesized and characterized. To test the feasibility of accessing Pt(IV) complexes by oxidizing their Pt(II) precursors, the previously reported ((t)bpy)Pt(R)(2) (R = Me and Ph) systems were oxidized with I(2) to yield ((t)bpy)Pt(R)(2)(I)(2). The analogous reaction with ((t)bpy)Pt(Me)(NHPh) and MeI yields the corresponding ((t)bpy)Pt(Me)(2)(NHPh)(I) complex. Reaction of ((t)bpy)Pt(Me)(NHPh) and phenylacetylene at 80 °C results in the formation of the Pt(II) phenylacetylide complex ((t)bpy)Pt(Me)(C≡CPh). Kinetic studies indicate that the reaction of ((t)bpy)Pt(Me)(NHPh) and phenylacetylene occurs via a pathway that involves [((t)bpy)Pt(Me)(NH(2)Ph)][TFA] as a catalyst. The reaction of H(2) with ((t)bpy)Pt(Me)(NHPh) ultimately produces aniline, methane, (t)bpy, and elemental Pt. For this reaction, mechanistic studies reveal that 1,2-addition of dihydrogen across the Pt-NHPh bond to initially produce ((t)bpy)Pt(Me)(H) and free aniline is catalyzed by elemental Pt. Heating the cationic complexes [((t)bpy)Pt(NHPh)(py)][BAr'(4)] and [((t)bpy)Pt(OPh)(py)][BAr'(4)] in C(6)D(6) does not result in the production of aniline and phenol, respectively. Attempted synthesis of a cationic system analogous to [((t)bpy)Pt(NHPh)(py)][BAr'(4)] with ligands that are more labile than pyridine (e.g., NC(5)F(5)) results in the formation of the dimer [((t)bpy)Pt(μ-NHPh)](2)[BAr'(4)](2). Solid-state X-ray diffraction studies of the complexes ((t)bpy)Pt(Me)(NHPh), [((t)bpy)Pt(NH(2)Ph)(2)][OTf](2), ((t)bpy)Pt(NHPh)(2), ((t)bpy)Pt(OPh)(2), ((t)bpy)Pt(Me)(2)(I)(2), and ((t)bpy)Pt(Ph)(2)(I)(2) are reported.

Photophysical and Theoretical Studies of Ruthenium(II)−Acetylide and −Cyanide Complexes with Aromatic Diimine and Trithiacyclononane

Ruthenium(II)−chloride, −cyanide, and −phenylacetylide complexes bearing aromatic diimine (2,2′-bipyridine (bpy), 4,4′-dimethyl-2,2′-bipyridine (Me2bpy), or dipyrido-[3,2-f:2′,3′-h]-quinoxaline (dpq)) and cyclic tridentate thioether 1,4,7-trithiacyclononane ([9]aneS3) have been prepared. The crystal structures of [Ru([9]aneS3)(bpy)(C≡N)](PF6) and [Ru([9]aneS3)(diimine)(C≡CPh)](PF6) (diimine = bpy and Me2bpy) reveal Ru−C distances of 2.024(4) and 2.030(3)−2.038(2) A, respectively. The oxidation waves for the complexes are attributed to the removal of an electron from a [dπ(Ru) + L] hybrid orbital (L = −Cl, −C≡N, and −C≡CPh), whereas the reduction waves are assigned as reduction of the aromatic diimine. The lowest-energy dipole-allowed absorptions for the complexes (λmax = 403−475 nm, emax = (3−5) × 103 dm3 mol−1 cm−1) are assigned as [dπ(RuII) + L] → π*(diimine) charge transfer transitions. All the acetylide complexes weakly emit at λmax = 663−680 nm in CH3CN at 298 K with quantum yield = (5−8) × 10−4 (λex...

Reactivity studies of highly electrophilic ruthenium complexes

The 16-electron, coordinatively unsaturated, dicationic ruthenium complex [Ru(P(OH) 2(OMe))(dppe) 2][OTf] 2 ( 1a) brings about the heterolysis of the C–H bond in phenylacetylene to afford the phenylacetylide complex trans-[Ru(C CPh)(P(OH) 2(OMe))(dppe) 2][OTf] ( 2). The phenylacetylide complex undergoes hydrogenation to give a ruthenium hydride complex trans-[Ru(H)(P(OH) 2(OMe))(dppe) 2][OTf] ( 3) and phenylacetylene via the addition of H 2 across the Ru–C bond. The 16-electron complex also reacts with HSiCl 3 quite vigorously to yield a chloride complex trans-[Ru(Cl)(P(OH) 2(OMe))(dppe) 2][OTf] ( 4). On the other hand, the other coordinatively unsaturated ruthenium complex [Ru(P(OH) 3)(dppe) 2][OTf] 2 ( 1b) reacts with a base N-benzylideneaniline to afford a phosphonate complex [Ru(P(O)(OH) 2)(dppe) 2][OTf] ( 5) via the abstraction of one of the protons of the P(OH) 3 ligand by the base. The phenylacetylide, chloride, and the phosphonate complexes have been structurally characterized. The phosphonate complex reacts with H 2 to afford the corresponding dihydrogen complex trans-[Ru(η 2-H 2)(P(O)(OH) 2)(dppe) 2][OTf] ( 5- H 2 ). The intact nature of the H–H bond in this species was established using variable temperature 1H spin–lattice relaxation time measurements and the observation of a significant J(H,D) coupling in the HD isotopomer trans-[Ru(η 2-HD)(P(O)(OH) 2)(dppe) 2][OTf] ( 5- HD).

Experimental Evidence for Magnetic Exchange in Di- and Trinuclear Uranium(IV) Ethynylbenzene Complexes

We report the preparation and magnetic property investigations of a structurally related family of mono-, di-, and trinuclear U(IV) aryl acetylide complexes. The reaction between [(NN'(3))UCl] and lithiated aryl acetylides leads to the formation of the hexacoordinate complexes [(NN'(3))U(CCPh)(2)(Li.THF)] (1) and [(NN'(3))(2)U(2)(p-DEB)(THF)] (2) as red-brown and yellow-green crystalline solids, respectively. In contrast, combining the uranacycle [(bit-NN'(3))U] (bit-NN'(3) = [N(CH(2)CH(2)NSi(t)BuMe(2))(2)(CH(2)CH(2)Si(t)BuMeCH(2)]) with stoichiometric amounts of mono-, bis-, and tris(ethynyl) benzenes affords the yellow-green pentacoordinate arylacetylide complexes [(NN'(3))U(CCPh)] (3), [(NN'(3))(2)U(2)(m-DEB)] (4), [(NN'(3))(2)U(2)(p-DEB)] (5), and [(NN'(3))(3)U(3)(TEB)] (6), where NN'(3) = [N(CH(2)CH(2)NSi(t)BuMe(2))(3)]. The measured magnetic susceptibilities for 1-6 trend toward non-magnetic ground states at low temperatures. Nevertheless, the di- and trinuclear pentacoordinate compounds 4-6 appear to display weak magnetic communication between the uranium centers. This communication is modeled by fitting of the direct current (DC) magnetic susceptibility data, using the spin Hamiltonian H = -2J(S(i) x S(j)). These results are consistent with weak ferromagnetic coupling for complexes 4-6 (J = 4.76, 2.75, and 1.11 cm(-1), respectively), while the fit for 2 is consistent with a near-negligible exchange interaction (J = -0.05 cm(-1)). Geometry-optimized Stuttgart/6-31 g* B3LYP hybrid DFT calculations were carried out (spin-orbit coupling omitted) on model complexes of 3-5. The mononuclear complex shows a triplet ground state with singly occupied degenerate f orbitals. The meta- and para-bridged species are computed to show very weak ferro- and antiferromagnetic coupling, respectively. All three complexes show only small net spin density on the acetylide-containing ligands. The monomeric phenylacetylide complex 3 undergoes a reversible redox couple at -1.02 V versus [Cp(2)Fe](+/0), assignable to an oxidation of U(IV) to U(V).

Solution luminescence from chloro(2,2′:6′,2″-terpyridine)platinum(II) chloride in micelles

Abstract Previously characterized as being non-luminescent in room-temperature fluid solution, the coordination compound chloro(2,2′:6′,2″-terpyridine)platinum(II) chloride can display two types of luminescence in certain microenvironments. In aqueous solutions of anionic and neutral surfactants having concentrations near or above their critical micelle concentration, [Pt(terpy)Cl]Cl (10–50 μM) displays broad emission centered at ∼610 nm that is characterized as metal-to-ligand charge transfer phosphorescence (3MLCT). In high concentration (10–100 mM) solutions having no surfactant, [Pt(terpy)Cl]Cl aggregates form. Excitation in the 470–540 nm region results in a long-wavelength emission centered at ∼720 nm that is characterized as metal–metal-to-ligand charge transfer phosphorescence (3MMLCT). This emission can also be detected in lower concentration solutions (10–50 μM) with surfactant concentration below its critical micelle concentration. Enhancement of 3MLCT luminescence is also found for the related phenylacetylide complex cation [Pt(terpy)(C CPh)]+ in micelles of the anionic surfactant sodium dodecyl sulfate.

Synthesis and photophysics of 4′-R-2,2′;6′,2″-terpyridyl (R = Cl, CN, N(CH3)2) platinum(II) phenylacetylide complexes

Platinum terpyridyl (tpy) phenylacetylide complexes with -Cl, -CN, and -NMe(2) substituents on the 4'-position of the tpy ligand were synthesized and characterized. Their photophysical properties were systematically investigated. In addition, theoretical electronic structure calculations using density functional theory (DFT) and time-dependent (TD-DFT) approaches were carried out for complexes and ; the results of these calculations provided additional information on the nature of the electronic structures of the low-lying electronic states of these complexes, including the electron density distribution and the composition of the frontier molecular orbitals. Complexes exhibit moderately intense charge-transfer bands in the visible region, which are assigned to the (1)MLCT/(1)LLCT transitions. In comparison to their corresponding chloride complexes , these charge-transfer bands become broadened and red-shifted. Complexes emit at room temperature in CH(3)CN and CH(2)Cl(2) solutions and at 77 K in butyronitrile glassy solutions. At room temperature, the emission is tentatively attributed to (3)MLCT for and , and to a mixture of (3)MLCT/(3)ILCT/(3)pi,pi* for . Due to the admixture of (3)ILCT/(3)pi,pi* characters in its emitting state, displays a much higher emission quantum yield and longer emission lifetime compared to and . Replacing the chloride co-ligand in by phenylacetylide co-ligand clearly enhances the emission and prolongs the lifetime. exhibit a broad and moderately intense triplet excited-state absorption in the visible to the NIR region, with large excited-state absorption coefficients and moderately high triplet excited state quantum yields. Therefore, complexes , especially , have potential applications in organic light emitting devices (OLED) and as reverse saturable absorbing materials.

4′-(5′′′-R-Pyrimidyl)-2,2′:6′,2′′-terpyridyl (R = H, OEt, Ph, Cl, CN) Platinum(II) Phenylacetylide Complexes: Synthesis and Photophysics

A series of new square-planar 4'-(5'''-R-pyrimidyl)-2,2':6',2''-terpyridyl platinum(II) phenylacetylide complexes ( 1a- 5a) bearing different substituents (R = H, OEt, Ph, Cl, CN) on the pyrimidyl ring have been synthesized and characterized. The electronic absorption, photoluminescence, and triplet transient difference absorption spectra were investigated. All of the complexes exhibit broad, moderately strong absorption between 400 and 500 nm that can be tentatively assigned to the metal-to-ligand charge transfer ( (1)MLCT) transition, possibly mixed with some ligand-to-ligand charge transfer ( (1)LLCT) character. Photoluminescence arising from the (3)MLCT state was observed both in fluid solutions at room temperature and in a rigid matrix at 77 K. The (1)MLCT/ (1)LLCT absorption bands and the (3)MLCT emission bands for 1a- 5a red-shift in comparison to those of the corresponding 4'-toly-2,2':6',2''-terpyridyl platinum(II) phenylacetylide complex. In addition, the energies of the (1)MLCT/ (1)LLCT absorption and the (3)MLCT emission bands exhibit a linear correlation with the Hammett constant (sigma p) of the 5'''-substituent on the pyrimidyl ring. The lifetime of the (3)MLCT emission at room temperature is governed by the energy gap law. The triplet transient difference absorption spectra of 1a- 5a exhibit a broad absorption band from 500 to 800 nm, and a bleaching band between 420 and 500 nm. Complex 5a, which contains the -CN substituent, exhibits a lower-energy triplet absorption band at 785 nm and a shorter lifetime (130 ns) in CH 3CN than 2a, which has the -OEt substituent, does (lambda T1-Tn (max) = 720 nm, tau T = 660 ns). The triplet excited-state absorption coefficients at the band maxima for 1a- 5a vary from 36 600 L.mol (-1).cm (-1) to 115 090 L.mol (-1).cm (-1), and the quantum yields of the triplet excited-state formation range from 0.19 to 0.66. All complexes exhibit a moderate nonlinear transmission for nanosecond laser pulses at 532 nm. Moreover, these complexes can generate singlet oxygen efficiently in air-saturated CH 3CN solutions, with the singlet oxygen generation quantum yield (Phi Delta) varying from 0.24 to 0.46.

Theoretical studies upon the electronic structures and spectroscopic properties for a series of luminescent terpyridyl platinum(II) phenylacetylide complexes

A comprehensive calculations were carried out to get a deep insight into the ground- and excited-state electronic structures and the spectroscopic properties for a series of [Pt(4-X–trpy)C CC 6H 4R] + complexes (trpy = 2,2′,6′,2″-terpyridine; X = H, R = NO 2 ( 1), Cl ( 2), C 6H 5 ( 3) and CH 3 ( 4); R = Cl, X = CH 3 ( 5) and C 6H 5 ( 6)). MP2 (second-order Møller–Plesset perturbation) and CIS (single-excitation configuration interaction) methods were employed to optimize the structures of 1–6 in the ground and excited states, respectively. The investigation showed that substituted phenylacetylide and trpy ligands only give rise to a small variation in geometrical structures but lead to a sizable difference in the electronic structures for 1–6 in the ground and excited states. The introduction of electron-rich groups into the phenylacetylide and/or terpyridyl ligands produces two different low-lying absorptions for 1 and 2–6, i.e., Pt(5d) → π ∗(trpy) metal-to-ligand charge transfer (MLCT) mixed with π → π ∗(C CPh) intraligand charge transfer (ILCT) for 1 and Pt(5d)/π(C CPh) → π ∗(trpy) charge transfer (MLCT and LLCT) for 2– 6. Remarkable electronic resonance on the whole Pt–C CPh–NO 2 moiety for 1 may be responsible for the difference. Solvatochromism calculation revealed that only LLCT/MLCT transitions showed the solvent dependence, consistent with the experimental observations.

Probing the Effect of the Ligand X on the Properties and Catalytic Activity of the Complexes RuHX(diamine)(PPh3)2 (X = OPh, 4-SC6H4OCH3, OPPh2, OP(OEt)2, CCPh, NCCHCN, CH(COOMe)2; diamine = 2,3-Diamino-2,3-dimethylbutane, (R,R)-1,2-Diaminocyclohexane)

The reactivity of the ruthenium−amido bond in RuH(NH2CMe2CMe2NH)(PPh3)2 (1) toward weak acids HX and the influence of the X group on the catalytic activity of the resulting complex are explored here. Complex 1 reacts with the weak acids HX (X = OPh, 4-SC6H4OMe, OPPh2, OP(OEt)2, CCPh, NCCHCN, CH(COOMe)2) to form complexes of the type RuHX(tmen)(PPh3)2 (tmen = 2,3-diamino-2,3-dimethylbutane). The complexes with X = PhOH···OPh, 4-SC6H4OMe, OP(OEt)2, CCPh, CH(COOMe)2 have been characterized by X-ray crystallography. The X group is situated trans to the hydride in all cases and is bonded to ruthenium via the donor atoms O, S, P, C, and O, respectively. The phenol in the phenoxide adduct RuH(PhOH···OPh)(tmen)(PPh3)2 bridges via hydrogen bonds between the alkoxide oxygen and an amino hydrogen to form a six-membered RuO···HO···HN ring. One carbonyl oxygen of the malonate bonds to the Ru, while the other accepts a hydrogen bond from an amino hydrogen. The analogous complexes RuHX(dach)(PPh3)2 (dach = (R,R)-1,2-diaminocyclohexane) were synthesized by the reaction of RuHCl(dach)(PPh3)2 (2) with an equimolar amount of potassium tert-butoxide and HX. For all of the complexes the Ru−H vibrational frequency and the 1H NMR chemical shift of Ru−H correlate with the electronegativity of the trans atom X. The amido complex 1 and the complexes with X = CH(COOMe)2 and OPh are active catalysts for the Michael addition of dimethyl malonate to 2-cyclohexen-1-one. RuH(NCCHCN)(tmen)(PPh3)2 reacts with the Michael acceptor 2-cyclohexen-1-one to give RuH(NCC(C6H9O)CN)(tmen)(PPh3)2, a trapped Michael adduct that has been characterized by X-ray crystallography. On the basis of these observations a catalytic cycle for the Michael addition reactions is proposed that involves the addition of the C−H bond of the Michael donor to the Ru−N bond followed by attack on the Michael acceptor and elimination of the Michael adduct, possibly by a 1,3-proton migration as observed for the malononitrile adduct. Only the complexes with X = H, CCPh are catalysts or precatalysts for the hydrogenation of neat acetophenone to 1-phenylethanol in the absence of added base under 10 atm of H2 at 20 °C. Evidence is provided that the phenylacetylide complexes are precatalysts that are converted to the active trans-dihydride catalysts (X = H).