Intraligand Transitions Research Articles

Sensitizing Tb(III) and Eu(III) emission with triarylboron functionalized 1,3-diketonato ligands.

Four BMes2Ar (Mes = mesityl, Ar = phenyl or duryl) functionalized 1,3-diketonato ligands have been investigated for use in selective sensitization of Tb(III) and Eu(III) emission. These ligands have the general formula of [R1C(O)CR2C(O)R3](-) (R1 = Ph, R2 = H, R3 = p-Ph-BMes2, L1; R1 = R3 = p-Ph-BMes2, R2 = H, L2; R1 = R3 = Me, R2 = p-Ph-BMes2, L3; R1 = R3 = Me, R2 = p-duryl-BMes2, L4) and belong to class I (L1 and L2) and class II (L3 and L4), respectively. In class I, the boron unit is conjugated with the phenyl linker and the diketone backbone, while in class II, the boron unit, the linker unit, and the diketone unit are nonconjugated with a mutually orthogonal arrangement. To understand the impact of the location of the BMes2Ar unit on the electronic properties of the 1,3-diketone molecules and their ability in activating lanthanide emission, the difluoroboron chelate compounds (1-BF2 to 4-BF2) of ligands L1-L4 were synthesized and examined. The class I ligands were effective in activating Eu(III) emission, while the class II ligands were effective in activating Tb(III) emission. Four Ln(III) complexes, 1Eu, 2Eu, 3Tb, and 4Tb, based on the L1-L4 ligands, respectively, were prepared and examined. The emission quantum efficiency of 1Eu and 2Eu is low (Φ(Eu) ≤ 0.01 in THF, 0.07-0.13 in the solid state), but can be greatly enhanced by the addition of fluoride ions. In contrast, the complex 4Tb has a moderate emission efficiency (Φ(Tb) = 0.14 in THF, 0.47 in the solid state) and experiences a distinct emission quenching upon the addition of fluoride. The selective sensitization of Eu(III) and Tb(III) by L1-L4 and the distinct luminescent response of their Ln(III) complexes toward fluoride ions are caused by the distinct intraligand charge transfer transitions of the two different classes of ligands involving the BMes2 unit.

Crystal structures, spectra properties and DFT calculations studies on 4-phenyl-1-(3-phenylallylidene)thiosemicarbazide and its Ni(II) complex

4-Phenyl-1-(3-phenylallylidene)thiosemicarbazide (HL) and its metal complex of NiL2 have been synthesized. For them, elemental analysis, IR and X-ray single crystal diffraction have been carried out. In complex NiL2, the central Ni2+ ion coordinates with two deprotonated ligands of L− and adopts a distorted square planar configuration with the Ni2+ ion being located at the inversion center. The thermal analyses result shows that complex NiL2 undergoes two decomposition processes. For the title compounds, DFT calculations of the structures and natural population analysis (NPA) have been performed at B3LYP/LANL2DZ level of theory. The predicted geometric parameters are compared with the experimental values and they are supported each other. By using TD-DFT method, electron spectra of ligand HL and complex NiL2 have been predicted, which suggest the B3LYP/LANL2DZ method can approximately simulate the electron spectra for the system presented here. The NPA results indicate that, for ligand HL, the electronic absorption spectra are mainly assigned to n–π∗ and π–π∗ electron transitions, while for the complex NiL2, the electronic transitions are mainly derived from the contribution of an intra-ligand (IL) transition, a metal-to-ligand charge transfer (MLCT) transition and a d–d transition. Based on vibrational analysis, thermodynamic properties for ligand HL and complex NiL2 at different temperatures have been obtained.

Effects of Extended π-Conjugation in Phenanthroline (N∧N) and Phenylpyridine (C∧N) Ligands on the Photophysics and Reverse Saturable Absorption of Cationic Heteroleptic Iridium(III) Complexes

Five new iridium(III) complexes (3,8-R-Phen)Ir(2-(3-R′-phenyl)pyridine)2 (1, R = fluoren-2-yl, R′ = H; 2, R = 7-benzothiazolylfluoren-2-yl, R′ = H; 3, R = H, R′ = fluoren-2-yl; 4, R = H, R′ = 7-benzothiazolylfluoren-2-yl; 5, R = R′ = 7-benzothiazolylfluoren-2-yl) with fluoren-2-yl or 7-benzothiazolylfluoren-2-yl substituent on the 2-phenylpyridine (C∧N) and/or phenanthroline (N∧N) ligands were synthesized and characterized. Their photophysical properties were investigated systematically via UV–vis absorption, emission, and transient difference absorption spectroscopy. Time-dependent density functional theory (TDDFT) calculations were performed to complement the experimental data and aid in our understanding of the characters of optical transitions. In addition, reverse saturable absorption was demonstrated at 532 nm for all complexes using nanosecond laser pulses. All complexes possess a weak low-energy tail that is attributed to 1,3MLCT (metal-to-ligand charge transfer)/1,3LLCT (ligand-to-ligand charge transfer) transitions. The major absorption bands below 475 nm for 1–5 arise from the 1π,π* and intraligand (1ILCT) transitions within the N∧N or C∧N ligands. Attachment of fluoren-2-yl or 7-benzothiazolylfluoren-2-yl substituents on N∧N ligand results in stronger red-shifts of the main absorption band to 400 and 408 nm for 1 and 2, respectively, as compared to 321 and 361 nm in complexes 3 and 4 with the same substituents on the C∧N ligands. In contrast, the 1,3MLCT/1,3LLCT transitions in 1 and 2 are just slightly red-shifted as compared to those in 3 and 4. The emission of complexes 1 and 2 is attributed to the N∧N ligand-centered 3π,π* state with some admixture of 3MLCT/3ILCT/3LLCT characters for 1. In contrast, the emission of 3 and 4 emanates exclusively from the 3MLCT/3LLCT states. For complex 5, which contains 7-benzothiazolylfluoren-2-yl substituents on both the C∧N and the N∧N ligands, the emission predominantly arises from the 3MLCT/3LLCT states with a small portion of N∧N ligand-localized 3π,π* character. All complexes exhibit broadband triplet excited-state absorption in the visible to the near-IR region, with the major absorption bands bathochromically shifted in 1 and 2 as compared to those in 3 and 4. The stronger excited-state absorption leads to dramatic reverse saturable absorption (RSA) at 532 nm for nanosecond laser pulses. The RSA strength decreases as 5 ≈ 2 > 4 ≈ 1 > 3, which is primarily determined by the ratio of the triplet excited-state absorption cross section relative to that of the ground state. Extended π-conjugation in the N∧N ligand obviously increases the RSA of complexes 1, 2, and 5 in comparison to those with π-conjugated substituents only on the C∧N ligands (3 and 4).

Synthesis, Characterization, and Luminescence Studies of Discrete Polynuclear Gold(I) Sulfido and Selenido Complexes with Intramolecular Aurophilic Contacts

The synthesis, characterization, and photophysical and photochemical properties of a family of high-nuclearity gold(I) chalcogenides, specifically, the gold(I) sulfido and selenido complexes containing different bridging diphosphine ligands with nuclearities of ten ([Au10{μ-Ph2PN(R)PPh2}4(μ3-E)4](2+)) and six ([Au6{μ-Ph2PN(R)PPh2}3(μ3-E)2](2+)), are reported. The X-ray crystal structures of the complex cations of Au10 and Au6 are found to be propeller-like structures and distorted cubane structures, respectively, with the presence of short intramolecular gold···gold distances. The complexes show intense green and/or orange phosphorescence upon photoexcitation in the solid state and in solution at ambient and low temperature. The emission properties are found to be strongly dependent on the nuclearities and the chalcogenido ligands, but are rather insensitive to the substituents on the bis(diphenylphosphino)amines. The emissions are tentatively assigned to originate from the excited states derived from the phosphine-centered intraligand (IL) transition or metal-centered (ds/dp) mixed with ligand-to-metal-metal charge transfer (LMMCT) (E→Au) transition. The photochemical properties of the complexes were also studied by transient absorption spectroscopy.

Photoinduced Dimerization Reaction Coupled with Oxygenation of a Platinum(II)–Hydrazone Complex

Photoreactivities of Ni(II)- and Pt(II)-hydrazone complexes, [NiCl(L)] (Ni1) and [PtCl(L)] (Pt1), respectively [HL = 2-(diphenylphosphino)benzaldehyde-2-pyridylhydrazone], were investigated in detail via UV-vis absorption, (1)H nuclear magnetic resonance (NMR) spectroscopy, and electrospray ionization time-of-flight (ESI-TOF) mass spectrometry; the two photoproducts obtained from the photoreaction of Pt1 were also successfully identified via X-ray analysis. The absorption bands of the Ni1 and Pt1 complexes were very similar, centered around 530 nm, and were assigned as an intraligand charge transfer transition of the hydrazone moiety. The absorption spectrum of Pt1 in a CH3CN solution changed drastically upon photoirradiation (λ = 530 nm), whereas no change was observed for Ni1. (1)H NMR and ESI-TOF mass spectra under various conditions suggested that the photoexcited Pt1* reacts with dissolved dioxygen to form a reactive intermediate, and the ensuing dark reactions afforded two different products without any decomposition. In contrast to the simple photo-oxidation of HL to form a phosphine oxide HL(P═O), the X-ray crystallographic analyses of the photoproducts clearly indicate the formation of a mononuclear Pt complex with the oxygenated hydrazone ligand (Pt1O) and a dinuclear Pt complex with the oxygenated and dimerized hydrazone ligand (Pt2). The photosensitized reaction in the presence of an (1)O2-generating photosensitizer, methylene blue (MB), also produced Pt1O and Pt2, indicating that the reaction between (1)O2 and ground-state Pt1 is the important step. In a highly viscous dimethyl sulfoxide solution, Pt1 was slowly, but quantitatively, converted to the mononuclear form, Pt1O, without the formation of the dinuclear product, Pt2, upon photoirradiation (and in the reaction photosensitized by MB), suggesting that this photoreaction of Pt1 involves at least one diffusion-controlled reaction. On the other hand, the same complexes Pt1O and Pt2 were also produced in the degassed solution, probably because of the reaction of the photoexcited Pt1* with the biradical character and H2O.

Optical properties of bicyclometalated Ir(III) and Rh(III) complexes of benzo[h]quinoline with (N∧S)− and (N∧O)− chelating ligands

[M(bzq)2(N∧X)] complexes (M = Rh(III), Ir(III); (bzq)− is the deprotonated form of benzo[h]quinoline, and (N∧X)− are 2-thiolpyridine, 2-hydroxypyridine, and 2-thiolbenzothiazole ions) are studied by absorption and emission spectroscopy and voltammetry. The long-wavelength absorption bands of [Rh(bzq)2(N∧X)] in the range of 420–424 nm are attributed to the optical metal-to-ligand charge transfer (MLCT) transitions, while the low-temperature (77 K) phosphorescence in the range of 490–610 nm is assigned to the intraligand (IL) transition of the {Rh(bzq)2} metal-complex fragment. The phosphorescence of the [Ir(bzq)2(N∧X)] complexes in liquid solutions in the range of 585–675 nm is assigned to the radiative MLCT transition, while the low-temperature (77 K) phosphorescence occurs from the thermally nonequilibrium MLCT and IL excited states of the {Ir(bzq)2} metal-complex fragment.

A 3D Porous Coordination Polymer from Tetrazole Ligand and Cd(II): Crystal Structure, Luminescent Property and Adsorption of Methanol and Water

An unusual tetrazole-based Cd(II) coordination polymer, [Cd(4-tzba)(H2O)]n (tzba = 4-(tetrazolyl)benzenecarboxylic acid) (1), was synthesized by hydrothermal reaction and structurally characterized by single-crystal X-ray diffraction. The structure of 1 contains distorted octahedral cadmium centers coordinated by four different tzba2− ligands and a water molecule. All the tzba2− ligands display coordination of type, μ4-κN1:κN3:κN4:κO1, O2, which connects four Cd(II) atoms to form an intricate 3-D network. There are three kinds of apertures in the structure of 1; two helical channels and a hexagonal aperture are observed along different axes. Polymer 1 exhibits selective gas adsorption behavior for methanol, ethanol and water. In addition, 1 shows blue photoluminescence mainly arising from intraligand transitions of the aromatic rings in the tbza2− ligand.

ReI–IrI bimetallic complexes based on a bis(chelating) ligand composed of 1,10-phenanthroline and N-heterocyclic carbene: Coordination chemistry and their application for optical indicator of CO gas

Mono complex [Cl(CO)3ReI(IL-2)](PF6) and bimetallic complexes Cl(CO)3ReI(IL-2)–IrI(Ligand)nCl, where IL-2=1,3-dimethyl-2,3-dihydro-1H-imidazo[4,5-f][1,10]phenanthroline-2-yl and Ligand=1,5-cyclooctadiene (n=1) or carbon monoxide (n=2), were synthesized, characterized, and applied to react with carbon monoxide. Bis(chelating) ligand, IL-2, has two coordinating sites, 1,10-phenanthroline and imidazolium moieties. These complexes display typical intraligand transition (π–π∗) and metal-to-ligand charge-transfer (MLCT) bands in the ultraviolet and visible regions, respectively. It was demonstrated that complex Cl(CO)3ReI(IL-2)–IrI(COD)Cl can be used as a carbon monoxide (CO) indicator because Cl(CO)3ReI(IL-2)–IrI(CO)2Cl, a CO-substituted bimetallic complex, displays distinct optical behaviors compared to those of Cl(CO)3ReI(IL-2)–IrI(COD)Cl.

Synthesis, structure, photoluminescence and theoretical calculation on a novel Zn(II) coordination polymer with (4,8)-connected topology

Abstract A new compound, namely [Zn2(pbdc)1.5(TAZ)]n 2nH2O (1 H2pbdc = terephthalic acid, HTAZ = 1H-1,2,4-triazole), has been hydrothermally synthesized from H2pbdc, HTAZ and Cd(II) salts. Single crystal X-ray diffraction analysis reveals that compound 1 represents an unprecedented (4,8)-connected 3D topological network. Notably, two TAZ ligands in uniform μ3-1,2,4 bridging mode connect four Zn(II) ions together, giving rise to a [Zn4(TAZ)2] metallo-ligand subunit, which are further bridged via pbdc ligands in two kinds of coordination modes, resulting in the final 3D complicated framework. The relevant density of states (DOS) calculation result showed that the luminescence of 1 mainly originates from HTAZ intraligand charge transition.

Ortho-ruthenation of 1-naphthalenyl in 1-naphthaldehyde 4-R-benzoylhydrazones: Ruthenium(III) CNO pincer complexes

In methanol, reactions of [Ru(PPh3)3Cl2], 1-naphthaldehyde 4-R-benzoylhydrazones (H2nabhR, where R = H, Me, OMe, Cl and NO2) and NaOAc in 1:1:2 mol ratio provide ortho-metallated ruthenium(III) complexes of general formula trans-[Ru(nabhR)(PPh3)2Cl] (1–5) in 50–58% yields. Elemental analysis, magnetic susceptibility, spectroscopic (IR, UV–Vis and EPR) and cyclic voltammetric measurements were used to characterize the complexes. Single crystal X-ray structures of 1 (R = H), 2 (R = Me) and 5 (R = NO2) show pincer like coordination mode of nabhR2−. The 1-naphthalenyl ortho-C, the azomethine-N and the amidate-O donor nabhR2−, two mutually trans PPh3 and the chloride assemble a distorted octahedral trans-CNOClP2 coordination sphere around the trivalent metal centre. In the electronic spectra, dichloromethane solutions of 1–5 display multiple strong bands within 506–272 nm due to ligand to metal charge transfer and intraligand transitions. The room temperature (298 K) magnetic moments (μeff) of 1–5 are within 1.92–1.99 μB and they display rhombic EPR spectra in frozen (130 K) dichloromethane–toluene (1:1). Cyclic voltammetry with dimethylformamide solutions of the complexes reveals ligand substituent sensitive Ru(III) → Ru(II) reduction and Ru(III) → Ru(IV) oxidation in the potential ranges −0.27 to −0.36 V and 0.94–1.13 V (vs. Ag/AgCl), respectively.

Synthesis, structure, theoretical calculation of electronic absorption spectrum, and spectroscopic property analysis of Cu(II) complex with pyrazine-2-carboxylic acid based on DFT theory

An octahedral Cu(II) complex with pc− and water, [Cu(pc)2(H2O)2] (Hpc = pyrazine-2-carboxylic acid), was synthesized and its geometric structure, electronic structure, electronic absorption spectrum, and spectroscopic properties were thoroughly investigated by X-ray crystallography, density functional theory (DFT), and time-dependent DFT (TDDFT) theoretical calculations. The geometric structure and electronic structure were studied in detail on the basis of DFT results, partial density of states (PDOS), and overlap population density of states (OPDOS) analyses. According to theory, the electronic spectrum is in the UV–Vis region, and the spectroscopic properties are ascribed to σ → (d x2−y2, d xy) ligand-to-metal charge transfer transition for strong absorption bands with charge transfer from pc− σ orbitals to Cu(II) d x2−y2 and d xy orbitals, and π/σ → π* intra-ligand charge transfer transition for weak absorption bands with charge transfer from pc− σ/π orbitals to pc− π* antibonding orbitals. The coordinative water is not associated the optical transitions. Moreover, the Cu(II) central d → d charge transfer bands may be hard to observe in the visible-light region owing to the transition-forbidden selection rule. Both the Cu(II)–O/N (pc−) and Cu(II)–O (H2O) interactions are mainly ionic, but not covalent.

Synthesis, photoluminescence and computational study of rhenium(I) diimine complexes with [1,3,4]oxadiazole substituted 2,2′-bipyridine ligands

Four bipyridine ligands substituted by the [1,3,4]oxadiazole moieties at different positions, 4,4′- bis(5-phenyl-[1,3,4]oxadiazol-2-yl)-2,2′-bipyridine (L1), 4,4′-bis[5-(4-tert-butyl-phenyl)-[1,3,4] oxadiazol-2-yl]-2,2′-bipyridine (L2), 5,5′-bis(5-phenyl-[1,3,4]oxadiazol-2-yl)-2,2′-bipyridine (L3), and 5,5′-bis[5-(4-tert-butyl-phenyl)-[1,3,4]oxadiazol-2-yl]-2,2′-bipyridine (L4), and their corresponding rhenium(I) Re(CO)3Cl(L) complexes (1–4) were synthesized and characterized by the elemental analysis, IR, 1H NMR and UV–vis spectroscopy. The complex 2 is also determined by the crystal structure analysis. In the UV–vis spectra complexes 1, 2 and 4 show intense spin-allowed intraligand (π→π*) transitions and weak metal to ligand charge-transfer dπ (Re)→π* (diimine) (MLCT) bands in THF solution. Complexes 1, 2 and 3 show efficient photoluminescent emission assigned to dπ (Re)→π* (diimine) MLCT phosphorescence at ambient temperature, and the different substitution position of [1,3,4]oxadiazole moieties in bipyridine ligands has a great effect on both absorption and emission properties of complexes. Among complexes 1, 2 and 3, the 4,4′-disubstituted complex 1 exhibits the strongest phosphorescence emission both in aerated THF solution (a quantum yield of 1.1%) and solid state. Meanwhile, the ground-state electronic structure and absorption spectra of 1–4 are investigated theoretically by DFT and TD-DFT methods.

Syntheses, crystal structures and fluorescent properties of two d 10-metal coordination polymers based on 1,5-naphthalenedisulfonic acid

The first examples of two d 10 metal coordination polymers based on 1,5-naphthalenedisulfonic acid and benzimidazole, namely, [Cd(bim)4(1,5-nds)] 1 and [Ag(bim)2]·½1,5-nds 2 (bim = benzimidazole, 1,5-nds = 1,5-naphthalenedisulfonic acid) were synthesized successfully under solvothermal conditions. Their structures were determined by single-crystal X-ray diffraction analyses and further characterized by elemental analyses, IR, TG-DSC, PXRD, UV–Vis, and DFT. 1 exhibits a 3D supramolecular structure which started from 1D helical chain. 2 also shows a 3D architecture which was assembled via π–π interactions and hydrogen bonds. The hydrogen bonds formed by 1,5-nds play an important role in increasing the dimensionality of architectures of 1 (from 1D to 3D) and 2 (from 0D to 1D). Moreover, both 1 and 2 show excellent luminescent properties, 335 nm for 1 (λ ex = 286 nm) and 341 nm and 389 nm for 2 (λ ex = 234 nm), and may be the suitable candidates of fluorescent materials. From UV–Vis spectra, the remarkable absorption peaks can be found at 276 nm for 1 and 271 nm for 2. The simulated UV–Vis spectra (290.30 nm for 1 and 271.64 nm for 2) by Gaussian 09 DFT correspond well with the experimental results. From the electron density distribution of frontier molecular orbitals, it is known that the two absorption bands are attributed to the intra-ligand electron transition from HOMO−26 to LUMO and from HOMO−3 to LUMO+1 for 1, from HOMO−1 to LUMO+18 and LUMO+19 for 2.

Tuning of the optical properties of chiral Schiff base Zn(II) complexes by substituents

Three new chiral Schiff base zinc(II) complexes, bis(N-R-1-phenylethyl-3-methoxysalicydenaminato) zinc(II), bis(N-R-1-naphthylethyl-3-methoxysalicydenaminato) zinc(II) and bis(N-R-1-naphthylethyl-5-methoxysalicydenaminato) zinc(II), have been prepared and characterized structurally. They are found to have a distorted square planar or compressed tetrahedral trans-[ZnN2O2] coordination geometry. Their UV–Vis and CD spectra exhibit intense intraligand transition bands, which are affected by the positions of the substituted methoxy groups of the aldehyde moieties rather than the extension of the π-conjugated ring (phenyl or naphthyl) groups of the amine moieties. A similar dependence of the molecular structures can also be found in the case of the fluorescence spectra, which is in agreement with a comparison with analogous zinc(II) complexes. The results of computational chemistry, which was performed to simulate UV–Vis and CD spectra for these complexes, suggest that the correlation between the effects of substitution and HOMO–LUMO gaps associated with the most intense intraligand transitions can be reasonably explained.

Two new three-dimensional metal–organic frameworks constructed from a semirigid V-shaped ligand with luminescent and topology studies

Two new compounds [Zn2L(OH)H2O]n (1) and [Cd(HL)]n (2) have been assembled from a semirigid V-shape ligand under hydrothermal conditions. The two compounds were determined by single-crystal X-ray diffraction analyses and further characterized by solid state emission spectra, IR spectra, and thermogravimetric analyses. Single crystal X-ray diffraction analyses show that both of the two compounds crystallize in space group P1¯ and display a three-dimensional (3D) structure with different topologies of fluorite topology for 1 and Au4Ho topology for 2. It is noteworthing that 1 has a novel Zn2 dinuclear unit containing only one bridging oxygen atom between two Zn atoms. Studies of photophysical properties reveal that 1 and 2 present luminescence, which can be ascribed to the emission of intraligand transition.

Heteroleptic diimine copper(i) complexes with large extinction coefficients: synthesis, quantum chemistry calculations and physico-chemical properties

Using the HETPHEN approach, five new heteroleptic copper(I) complexes composed of a push-pull 4,4'-styryl-6,6'-dimethyl-2,2'-bipyridine ligand and a bulky bis[(2-diphenylphosphino)phenyl]-ether (DPEphos) or a bis2,9-mesityl phenanthroline (Mes2Phen) were prepared and characterized by electronic absorption spectroscopy, electrochemistry, and TD-DFT calculations. These complexes exhibit very intense absorption bands in the visible region with extinction coefficient in the range of 5-7 × 10(4) M(-1) cm(-1). The analysis of the position, intensity and band shape indicates a strong contribution from an intra-ligand charge-transfer transition centered on the styrylbipyridine ligand along with MLCT transitions. These new complexes experimentally demonstrate that good light harvesting properties with bis-diimine copper(I) complexes are a reality if one chooses suitable ligands in the coordination sphere. This constitutes a milestone towards using bis-diimine copper(I) complexes for solar energy conversion (artificial photosynthesis and solar cells).

Polyrotaxane frameworks containing N,N′,N′′-(4,4′,4′′-nitrilotris(4,1-phenylene))triisonicotinamide: structural and luminescent properties

The reaction of a C3-symmetric tridentate ligand, N,N′,N′′-(4,4′,4′′-nitrilotris(4,1-phenylene))triisonicotinamide (L), with various d10-metal salts of CuI, Cu(SCN), and M(ClO4)2 (M = Zn, Cd) led to four metal–organic materials of {[(Cu2I2)(L)2]·4DMF·2MeOH}n (1), {[Cu(L)2(NCS)2]·3DMF}n (2), and {[M(L)2(ClO4)2]·4EtOH}n (M = Zn 3 and Cd 4), respectively, which have been isolated and structurally characterized by X-ray diffraction studies. The X-ray analysis revealed that the interlocking of the 1-D double-zigzag chains of 1–4 into the macrocycles of the adjacent chains generates a novel 2-D (1-D → 2-D) polyrotaxane framework. In these 2-D polyrotaxane frameworks, the C3-symmetric tridentate ligand, L, only adopts a μ2-bridging mode, and the third arm is free. In addition, 1–4 are all emissive with dual emissions (431–452 and 558–570 nm) in the solid state at room temperature and at 77 K, which are suggested to be due to an intraligand transition of L based on the high similarities in emission energies to that of L.

2D and 1D Coordination Polymers of Ag(I) Ions with 2,6-Naphthalenedicarboxylate and N–Donor Coligands

Two new Ag(I) coordination polymers [Ag2(mepyz)](2,6-ndc)] n (1) and [Ag4(4,4′-bipy)]4(2,6-ndc)2·8(H2O) (2) (where 2,6-ndcH2 = 2,6-napthalene dicarboxylic acid, mepyz = 2-methyl pyrazine and 4,4′-bipy = 4,4′-bipyridine) have been synthesized and characterized by single crystal X-ray diffraction analysis. Complex 1 displays a 2D rectangular grid architecture comprising short Ag···Ag interactions, while 2 is a 1D coordination polymer: both enlarge their dimensionality to 3D via weak interactions. Luminescence study performed on complexes as well on ligands shows metal perturbed intraligand CT transition. Two new luminescent coordination polymers of Ag(I) have been synthesized. The X-ray structural determination analysis revealed 2D and 1D coordination polymers that enlarge dimensionality to 3D via weak supramolecular interactions.

Cyclometalated rhodium complexes of phenyl- and diphenyl-substituted oxazole and thiazole luminophores

Cyclometaleted rhodium complexes of oxazole and thiazole luminophores [Rh(C∧N)2En]Cl [(C∧N)−, deprotonated forms of 2,5-diphenyloxazole, 2-phenylbenzothiazole, 2-(biphenyl-4-yl)-6-phenylbenzoxazole, and 2-(biphenyl-4-yl)-5-phenyloxazole; En — ethylenediamine] were obtained and characterized by the methods of 1H NMR, IR, and electron absorption and emission spectroscopy. Two cyclometallated ligands in the inner sphere of the complexes are in the cis-C,C positions. Cyclometallating of the luminophores results both in a red shift of intraligand π-π*-optical transitions (Δν ∼1.2 kK) as compared to free luminophores and in the appearance of a long-wave band (λmax 376–392 nm) of a mixed nature: metal-ligand charge transfer/intraligand transition. Alongside with the internal conversion to a low-energy state of the metal-ligand charge transfer/ intraligand transition, the emission degradation of photoexcitation energy results in the intraligand π-π*-fluorescence of the complexes (λmax 390–423 nm) at room temperature.

Rhenium(I) tricarbonyl complexes with multidentate nitrogen-donor derivatives

The reaction of [Re(CO)5X] (X=Cl, Br) with a series of six potentially multidentate nitrogen donor ligands (L1–L6) was studied. The ligands L1–L5 are coordinated bidentately in the neutral complexes of the type fac-[Re(CO)3X(L)] (1–5). The complex salt [Re(CO)3(L6)]Br (6) was formed by the reaction of [Re(CO)5Br] with 2-aminobenzaldehyde (aba), in which the tridentate ligand L6 was formed by the Schiff base condensation of three aba molecules. The crystal structures for complexes 1–6 were determined by X-ray single crystal diffraction. UV–Vis absorption spectra of the complexes show the intraligand and MLCT transitions. Electrochemical behaviour of the complexes was studied with cyclic voltammetry.