Phosphorescent, Cyclometalated Cinchophen-Derived Platinum Complexes: Syntheses, Structures, and Electronic Properties

The syntheses of nine new monometallic heteroleptic platinum complexes [Pt­(<b>L1–4</b>)­(acac)], [Pt­(<b>L1</b>)­(hmacac/hfacac)], [PtCl­(<b>L1</b>)­(py)], [Pt­(<b>L1</b>)­(8-Q)], [Pt­(<b>L1</b>)­(bpy)]­(PF₆) (where L1 = 2-phenyl-4-ethyl-quinolinecarboxylate; L2/L3 = <i>N</i>-functionalization of 2-phenyl-<i>N</i>-aryl/alkyl-quinoline-4-carboxamides; L4 = 2-phenyl-4-quinolinecarboxylic acid (cinchophen); acac = acetylacetonato; hmacac =2,2,6,6-tetramethyl-3,5-heptanedionate; hfacac = hexafluoroacetylacetonate; py = pyridine; 8-Q = 8-quinolinato; bpy =2,2′-bipyridine) are described from precursor dimeric Pt­(II) species via an intermediate DMSO adduct of the general form [PtCl­(<b>L1–4</b>)­(DMSO)]. Single crystal X-ray diffraction studies were undertaken on three complexes, [Pt­(<b>L1</b>)­(acac)], [PtCl­(<b>L1</b>)­(DMSO)], and [Pt­(<b>L1</b>)­(bpy)]­(PF₆). The structures show that the complexes each adopt a distorted square planar geometry (most severely in the case of [Pt­(<b>L1</b>)­(bpy)]­(PF₆)) with indications of intermolecular Pt–Pt interactions in one example. The complexes were investigated using ¹⁹⁵Pt­{¹H} NMR spectroscopy, revealing varied chemical shifts that were strongly dependent upon the specific coordination environment of Pt­(II). Luminescence studies showed the complexes possess a phosphorescent character with tunable emission wavelengths between 605 and 641 nm and luminescent lifetimes up to ∼450 ns. Supporting TD-DFT studies provided descriptions of the HOMO and LUMO energy levels of the key complex types, confirming an MLCT contribution to the lowest energy absorption that generally correlated well with the experimental spectra. The contribution of the Pt­(5d) center to the calculated HOMOs was strongly ligand dependent, whereas the LUMOs are generally localized over the quinoline component of the cyclometalated ligand

Synthesis, Structures, and Luminescent Properties of Uranyl Terpyridine Aromatic Carboxylate Coordination Polymers

Six novel uranyl terpyridine aromatic carboxylate coordination polymers, [UO₂(C₆H₂O₄S)­(C₁₅H₁₁N₃)] (<b>1</b>), [UO₂(C₆H₂O₄S)­(C₁₅H₁₀N₃Cl)]·H₂O (<b>2</b>), [UO₂(C₈H₄O₄)­(C₁₅H₁₁N₃)] (<b>3</b>), [UO₂(C₈H₄O₄)­(C₁₅H₁₀N₃Cl)] (<b>4</b>), [UO₂(C₁₂H₆O₄)­(C₁₅H₁₁N₃)] (<b>5</b>), and [UO₂(C₁₂H₆O₄)­(C₁₅H₁₀N₃Cl)] (<b>6</b>), were synthesized under solvothermal conditions and characterized by single-crystal and powder X-ray diffraction and luminescence and UV–vis spectroscopy. Compounds <b>1</b>, <b>2</b>, and <b>5</b> crystallize as molecular uranyl dimers, whereas compounds <b>3</b>, <b>4</b>, and <b>6</b> contain ladder motifs of uranyl centers. Fluorescence spectra of <b>1</b>–<b>4</b> show characteristic UO₂²⁺ emission, wherein bathochromic and hypsochromic shifts are noted as a function of organic species. In contrast, uranyl emission from <b>5</b> and <b>6</b> is quenched by the naphthalene dicarboxylic acid linker molecules

Synthesis, Structures, and Luminescent Properties of Uranyl Terpyridine Aromatic Carboxylate Coordination Polymers

Six novel uranyl terpyridine aromatic carboxylate coordination polymers, [UO₂(C₆H₂O₄S)­(C₁₅H₁₁N₃)] (<b>1</b>), [UO₂(C₆H₂O₄S)­(C₁₅H₁₀N₃Cl)]·H₂O (<b>2</b>), [UO₂(C₈H₄O₄)­(C₁₅H₁₁N₃)] (<b>3</b>), [UO₂(C₈H₄O₄)­(C₁₅H₁₀N₃Cl)] (<b>4</b>), [UO₂(C₁₂H₆O₄)­(C₁₅H₁₁N₃)] (<b>5</b>), and [UO₂(C₁₂H₆O₄)­(C₁₅H₁₀N₃Cl)] (<b>6</b>), were synthesized under solvothermal conditions and characterized by single-crystal and powder X-ray diffraction and luminescence and UV–vis spectroscopy. Compounds <b>1</b>, <b>2</b>, and <b>5</b> crystallize as molecular uranyl dimers, whereas compounds <b>3</b>, <b>4</b>, and <b>6</b> contain ladder motifs of uranyl centers. Fluorescence spectra of <b>1</b>–<b>4</b> show characteristic UO₂²⁺ emission, wherein bathochromic and hypsochromic shifts are noted as a function of organic species. In contrast, uranyl emission from <b>5</b> and <b>6</b> is quenched by the naphthalene dicarboxylic acid linker molecules

Gold(I) Complexes Derived from Alkynyloxy-Substituted Anthraquinones: Syntheses, Luminescence, Preliminary Cytotoxicity, and Cell Imaging Studies

A series of mono- and dimetallic Au­(I) triphenylphosphine complexes derived from 1,2-, 1,4-, and 1,8-dialkynyloxyanthraquinone have been prepared. The photophysical and cytotoxic behavior of the ligands and complexes have been explored, with all of the complexes showing both appreciable cytotoxicity against the MCF-7 carcinoma cell line and useful room-temperature anthraquinone-based visible luminescence, which allowed their successful application as fluorophores in cell imaging microscopy. The implications of the photophysical and toxicological properties for the design and investigation of gold-based anticancer agents are discussed

Gold(I) Complexes Derived from Alkynyloxy-Substituted Anthraquinones: Syntheses, Luminescence, Preliminary Cytotoxicity, and Cell Imaging Studies

A series of mono- and dimetallic Au­(I) triphenylphosphine complexes derived from 1,2-, 1,4-, and 1,8-dialkynyloxyanthraquinone have been prepared. The photophysical and cytotoxic behavior of the ligands and complexes have been explored, with all of the complexes showing both appreciable cytotoxicity against the MCF-7 carcinoma cell line and useful room-temperature anthraquinone-based visible luminescence, which allowed their successful application as fluorophores in cell imaging microscopy. The implications of the photophysical and toxicological properties for the design and investigation of gold-based anticancer agents are discussed

Closely-Related Zn^II₂Ln^III₂ Complexes (Ln^III = Gd, Yb) with Either Magnetic Refrigerant or Luminescent Single-Molecule Magnet Properties

The reaction of the compartmental ligand <i>N</i>,<i>N</i>′,<i>N</i>″-trimethyl-<i>N</i>,<i>N</i>″-bis­(2-hydroxy-3-methoxy-5-methylbenzyl)­diethylenetriamine (H₂L) with Zn­(NO₃)₂·6H₂O and subsequently with Ln­(NO₃)₃·5H₂O (Ln^III = Gd and Yb) and triethylamine in MeOH using a 1:1:1:1 molar ratio leads to the formation of the tetranuclear complexes {(μ₃-CO₃)₂[Zn­(μ-L)­Gd­(NO₃)]₂}·4CH₃OH (<b>1</b>) and­{(μ₃-CO₃)₂[Zn­(μ-L)­Yb­(H₂O)]₂}­(NO₃)₂·4CH₃OH (<b>2</b>). When the reaction was performed in the absence of triethylamine, the dinuclear compound [Zn­(μ-L)­(μ-NO₃)­Yb­(NO₃)₂] (<b>3</b>) is obtained. The structures of <b>1</b> and <b>2</b> consist of two diphenoxo-bridged Zn^II–Ln^III units connected by two carbonate bridging ligands. Within the dinuclear units, Zn^II and Ln^III ions occupy the N₃O₂ inner and the O₄ outer sites of the compartmental ligand, respectively. The remaining positions on the Ln^III ions are occupied by oxygen atoms belonging to the carbonate bridging groups, by a bidentate nitrate ion in <b>1</b>, and by a coordinated water molecule in <b>2</b>, leading to rather asymmetric GdO₉ and trigonal dodecahedron YbO₈ coordination spheres, respectively. Complex <b>3</b> is made of acetate–diphenoxo triply bridged Zn^IIYb^III dinuclear units, where the Yb^III exhibits a YbO₉ coordination environment. Variable-temperature magnetization measurements and heat capacity data demonstrate that <b>1</b> has a significant magneto–caloric effect, with a maximum value of −Δ<i>S</i>_m = 18.5 J kg^–1 K^–1 at <i>T</i> = 1.9 K and <b>B</b> = 7 T. Complexes <b>2</b> and <b>3</b> show slow relaxation of the magnetization and single-molecule magnet (SMM) behavior under an applied direct-current field of 1000 Oe. The fit of the high-temperature data to the Arrhenius equation affords an effective energy barrier for the reversal of the magnetization of 19.4(7) K with τ_o = 3.1 × 10^–6 s and 27.0(9) K with τ_o = 8.8 × 10^–7 s for <b>2</b> and <b>3</b>, respectively. However, the fit of the full range of temperature data indicates that the relaxation process could take place through a Raman-like process rather than through an activated Orbach process. The chromophoric L^2– ligand is able to act as an “antenna” group, sensitizing the near-infrared (NIR) Yb^III-based luminescence in complexes <b>2</b> and <b>3</b> through an intramolecular energy transfer to the excited states of the accepting Yb^III ion. These complexes show several bands in the 945–1050 nm region, corresponding to ²F_5/2→²F_7/2 transitions arising from the ligand field splitting of both multiplets. The observed luminescence lifetimes τ_obs are 0.515 and 10 μs for <b>2</b> and <b>3</b>, respectively. The shorter lifetime for <b>2</b> is due to the presence of one coordinated water molecule on the Yb^III center (and to a lesser extent noncoordinated water molecules), facilitating vibrational quenching via O–H oscillators. Therefore, complexes <b>2</b> and <b>3</b>, combining field-induced SMM behavior and NIR luminescence, can be considered to be dual magneto–luminescent materials

Alkynyl-naphthalimide Fluorophores: Gold Coordination Chemistry and Cellular Imaging Applications

A range of fluorescent alkynyl-naphthalimide fluorophores has been synthesized and their photophysical properties examined. The fluorescent ligands are based upon a 4-substituted 1,8-naphthalimide core and incorporate structural variations (at the 4-position) to tune the amphiphilic character: chloro (<b>L1</b>), 4-[2-(2-aminoethoxy)­ethanol] (<b>L2</b>), 4-[2-(2-methoxyethoxy)­ethylamino] (<b>L3</b>), piperidine (<b>L4</b>), morpholine (<b>L5</b>), 4-methylpiperidine (<b>L6</b>), and 4-piperidone ethylene ketal (<b>L7</b>) variants. The amino-substituted species (<b>L2</b>–<b>L7</b>) are fluorescent in the visible region at around 517–535 nm through a naphthalimide-localized intramolecular charge transfer (ICT), with appreciable Stokes’ shifts of ca. 6500 cm^–1 and lifetimes up to 10.4 ns. Corresponding two-coordinate Au­(I) complexes [Au­(L)­(PPh₃)] were isolated, with X-ray structural studies revealing the expected coordination mode via the alkyne donor. The Au­(I) complexes retain the visible fluorescence associated with the coordinated alkynyl-naphthalimide ligand. The ligands and complexes were investigated for their cytotoxicity across a range of cell lines (LOVO, MCF-7, A549, PC3, HEK) and their potential as cell imaging agents for HEK (human embryonic kidney) cells and Spironucleus vortens using confocal fluorescence microscopy. The images reveal that these fluorophores are highly compatible with fluorescence microscopy and show some clear intracellular localization patterns that are dependent upon the specific nature of the naphthalimide substituent

Using Substituted Cyclometalated Quinoxaline Ligands To Finely Tune the Luminescence Properties of Iridium(III) Complexes

The syntheses of five new heteroleptic iridium complexes <b>[Ir­(L</b>^{<b>1</b>–<b>4</b>}<b>)</b>_<b>2</b><b>(Diobpy)]­PF</b>_<b>6</b> (where Diobpy = 4,4′-dioctylamido-2,2′-bipyridine) and <b>[Ir­(L</b>^<b>3</b><b>)</b>_<b>2</b><b>(bpy)]­PF</b>_<b>6</b> (where L = <i>para</i>-substituted 2,3-diphenylquinoxaline cyclometalating ligands; bpy = 2,2′-bipyridine) are described. The structures of <b>[Ir­(L</b>^<b>3</b><b>)</b>_<b>2</b><b>(Diobpy)]­PF</b>_<b>6</b> and <b>[Ir­(L</b>^<b>3</b><b>)</b>_<b>2</b><b>(bpy)]­PF</b>_<b>6</b> show that the complexes each adopt a distorted octahedral geometry with the expected <i>trans</i>-N, <i>cis</i>-C arrangement of the cyclometalated ligands. Electrochemical studies confirmed subtle perturbation of the Ir^III/IV redox couple as a function of ligand variation. Luminescence studies showed the significant contribution of ³MLCT to the phosphorescent character with predictable and modestly tunable emission wavelengths between 618 and 636 nm. DFT studies provided approximate qualitative descriptions of the HOMO {located over the Ir­(5d) center (11–42%) and the phenylquinoxaline ligand (54–87%)} and LUMO {located over the ancillary bipyridine ligands (ca. 93%)} energy levels of the five complexes, confirming significant MLCT character. TD-DFT calculations indicate that UV–vis absorption and subsequent emission has substantial MLCT character, mixed with LLCT. Predicted absorption and emission wavelengths are in good general agreement with the UV–vis and luminescence experiments

Rain erosion resistance of infrared materials comparison of rotating arms and multiple impact jet apparatus (MIJA) measurements

Communication to : 8th European electromagnetic structures conference, Nottingham (GB), September 6-7, 1995SIGLEAvailable at INIST (FR), Document Supply Service, under shelf-number : 22419, issue : a.1995 n.169 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Using Substituted Cyclometalated Quinoxaline Ligands To Finely Tune the Luminescence Properties of Iridium(III) Complexes

The syntheses of five new heteroleptic iridium complexes <b>[Ir­(L</b>^{<b>1</b>–<b>4</b>}<b>)</b>_<b>2</b><b>(Diobpy)]­PF</b>_<b>6</b> (where Diobpy = 4,4′-dioctylamido-2,2′-bipyridine) and <b>[Ir­(L</b>^<b>3</b><b>)</b>_<b>2</b><b>(bpy)]­PF</b>_<b>6</b> (where L = <i>para</i>-substituted 2,3-diphenylquinoxaline cyclometalating ligands; bpy = 2,2′-bipyridine) are described. The structures of <b>[Ir­(L</b>^<b>3</b><b>)</b>_<b>2</b><b>(Diobpy)]­PF</b>_<b>6</b> and <b>[Ir­(L</b>^<b>3</b><b>)</b>_<b>2</b><b>(bpy)]­PF</b>_<b>6</b> show that the complexes each adopt a distorted octahedral geometry with the expected <i>trans</i>-N, <i>cis</i>-C arrangement of the cyclometalated ligands. Electrochemical studies confirmed subtle perturbation of the Ir^III/IV redox couple as a function of ligand variation. Luminescence studies showed the significant contribution of ³MLCT to the phosphorescent character with predictable and modestly tunable emission wavelengths between 618 and 636 nm. DFT studies provided approximate qualitative descriptions of the HOMO {located over the Ir­(5d) center (11–42%) and the phenylquinoxaline ligand (54–87%)} and LUMO {located over the ancillary bipyridine ligands (ca. 93%)} energy levels of the five complexes, confirming significant MLCT character. TD-DFT calculations indicate that UV–vis absorption and subsequent emission has substantial MLCT character, mixed with LLCT. Predicted absorption and emission wavelengths are in good general agreement with the UV–vis and luminescence experiments