Luminescence Ranging from Red to Blue: A Series of Copper(I)−Halide Complexes Having Rhombic {Cu2(μ-X)2} (X = Br and I) Units with N-Heteroaromatic Ligands

Interactions of 1,5-naphthyridine with Pd(en)Cl2 or [Pd(en)(H2O)2](NO3)2 in aqueous solution

The nature of the complexes formed in aqueous solution between either Pd(en)Cl2 or [Pd(en)(H2O)2](NO3)2 and 1,5-naphthyridine (1,5-NAP), where en is ethylenediamine, have been investigated by 1-D and 2-D (1)H NMR spectroscopy and potentiometric titration. Above pH 5.0, two major complexes have been identified with the stoichiometries of 2:1 and 1:1 (M:L ratio) as well as small amounts of a 1:2 complex and/or oligomer. The 2:1 complex consisted of a Pd(en)2+ moiety symmetrically bonded to each of the nitrogen atoms of the 1,5-NAP, as indicated by the presence of just three 1H NMR resonances in the aromatic region. The 1:1 complex had six resonances as a result of only one 1,5-NAP nitrogen atom being bonded to a Pd(en)2+ group. At pH<5, the uncomplexed nitrogen of the 1:1 and other singly bonded 1,5-NAP species became protonated and resulted in the formation of a large number of complexes. Job's method plots at pH 6 showed that the 1:1 complex is stable over a large concentration range. Above pH approximately 6 the 1:1 complex can dimerize via deprotonation of a water ligand on the Pd(en)2+ to form an hydoxo-bridged or oxo-bridged species. Evidence for this was observed in the upfield shifts of the resonances as the pH increased. The species distribution curve from potentiometric titrations and the NMR data were in good agreement at concentrations of 1-4 mM. NOESY data indicated that free 1,5-NAP ligand was exchanging with that in the 1:1 complex. In order to interpret the en region of the 1H NMR spectra, the spectra of [Pd(en)(H2O)2](NO3)2 in D2O at various pD were obtained.

Photophysical properties of highly luminescent copper(I) halide complexes chelated with 1,2-bis(diphenylphosphino)benzene

Studies on synthesis, structures, and photophysics have been carried out for a series of luminescent copper(I) halide complexes with the chelating ligand, 1,2-bis[diphenylphosphino]benzene (dppb). The complexes studied are halogen-bridged dinuclear complexes, [Cu(mu-X)dppb]2 (X = I (1), Br (2), Cl (3)), and a mononuclear complex, CuI(dppb)(PPh3) (4). These complexes in the solid state exhibit intense blue-green photoluminescence with microsecond lifetimes (emission peaks, lambdamax = 492-533 nm; quantum yields, Phi = 0.6-0.8; and lifetimes, tau = 4.0-10.4 mus) at 298 K. In 2-methyltetrahydrofuran (2mTHF) solutions at 298 K, only 1 and 4 show weaker emission (Phi = 0.009) with shorter lifetimes (tau = 0.35 and 0.23 mus) and red-shifted spectra (lambdamax = 543 and 546 nm). The emission in the solid state originates from the (M + X)LCT excited state with a distorted-tetrahedral conformation, in which emissive excited states, 1(M + X)LCT and 3(M + X)LCT, are in equilibrium with an energy difference of approximately 2 kcal/mol. On the other hand, the complexes in the 2mTHF solutions emit from the MLCT excited state with an energetically favorable flattened conformation in the temperature range of 298-130 K. The flattened geometry with equilibrated 1MLCT and 3MLCT states has a nonradiative rate at least 2 orders of magnitude larger than that of the distorted-tetrahedral geometry, leading to a much smaller emission quantum yield (Phi = 0.009) at 298 K. Since the flattening motion is markedly suppressed below 130 K, the emission observed in 2mTHF below 130 K is considered to occur principally from the (M + X)LCT state with a distorted-tetrahedral geometry. To interpret the photophysics of 1 and 4 in both the solid and solution states, we have proposed the "2-conformations with 2-spin-states model (2C x 2S model)". The electroluminescence device using (1) as a green emissive dopant showed a moderate EL efficiency; luminous efficiency = 10.4 cd/A, power efficiency = 4.2 lm/W at 93 cd/m(2), and maximum external quantum efficiency = 4.8%.

Di- and Tetranuclear Copper(I) Complexes Containing Phenylaminobis(phosphonite), PhN{P(OC6H4OMe-o)2}2, and Their Reactivity toward Bipyridyl Ligands

The aminobis(phosphonite) PhN(P(OC6H4OMe-o)2)2 (PNP; 1) reacts with 2 equiv of CuI to give a binuclear complex, Cu2(mu2-I)2(NCCH3)2(mu-PNP) (2), whereas similar reactions with CuCl and CuBr furnish tetranuclear "ladder"-type complexes, Cu4(mu2-X)2(mu3-X)2(mu-PNP)2 (3, X = Cl; 4, X = Br), in excellent yield. The complex 2 when heated under vacuum turns into the tetranuclear complex 5 in a reversible fashion. Similarly, the complexes 3 and 4 on dissolution in CH3CN dissociate reversibly into the corresponding binuclear complexes from which the tetrameric complexes can be readily regenerated. Treatment of 2 with excess of pyridine produces the heterosubstituted derivative, Cu2(mu2-I)2(C5H5N)2(mu-PNP) (6). The interaction of 2 with 2,2'-bipyridine in 1:1 and 1:2 ratios produces the mono- and disubstituted derivatives, Cu2(mu2-I)I(C10H8N2)(mu-PNP) (7) and [Cu2(mu2-I)(C10H8N2)2(mu-PNP)]I (8), respectively. The chloro and bromo analogues of 7 are prepared by treating the tetranuclear derivatives 3 and 4 with 2,2'-bipyridine. Reaction of 2 with 4,4'-bipyridine in the presence of AgOTf gives the cationic complex [Cu4(NCCH3)4(C10H8N2)2(mu-PNP)2](OTf)4 (9), whereas the complex [Cu2(NCCH3)2(mu-PNP)2](OTf)2 (10) was obtained from the reaction of 2 with 1 equiv of 1 and AgOTf. The reactions of 3 and 4 with 2 equiv of 4,4'-bipyridine in acetonitrile afford one-dimensional copper(I) coordination polymers [Cu2(mu2-X)2(mu-PNP)(C10H8N2)]n (13, X = Cl; 14, X = Br). The molecular structures of 2-4, 6-8, 12, and 14 are confirmed by X-ray crystallography.

Threaded structure and blue luminescence of (CuCN)20(Piperazine)7

The structurally unique and highly luminescent 20 : 7 complex of CuCN with piperazine (Pip) was formed under aqueous conditions; its structure reveals two interpenetrated 2D sub-networks in 6 : 1 ratio: (CuCN)2(Pip) and (CuCN)8(Pip), the latter consisting of Cu18(CN)16(Pip)2 macrocycles.

Increasing Structure Dimensionality of Copper(I) Complexes by Varying the Flexible Thioether Ligand Geometry and Counteranions

This work focuses on the systematic investigation of the influences of pyrimidine-based thioether ligand geometries and counteranions on the overall molecular architectures. A N-containing heterocyclic dithioether ligand 2,6-bis(2-pyrimidinesulfanylmethyl)pyridine (L1) and three structurally related isomeric bis(2-pyrimidinesulfanylmethyl)benzene (L2-L4) ligands have been prepared. On the basis of the self-assembly of CuX (X = I, Br, Cl, SCN, or CN) and the four structurally related flexible dithioether ligands, we have synthesized and characterized 10 new metal-organic entities, Cu4(L1)2I4 1, Cu4(L1)2Br4 2, [Cu2(L2)2I2.CH3CN]n 3, [Cu(L3)I]n 4, [Cu(L3)Br]n 5, [Cu(L3)CN]n 6, [Cu(L4)CN]n 7, [Cu2(L4)I2]n 8, [Cu2(L4)(SCN)2]n 9, and [[Cu6I5(L4)3](BF4).H2O]n 10, by elemental analyses, IR spectroscopy, and X-ray crystallography. Single-crystal X-ray analyses show that the 10 Cu(I) complexes possess an increasing dimensionality from 0D (1 and 2) to 1D (3-5) to 2D (6-9) to 3D (10), which indicates that the ligand geometry takes an essential role in the framework formation of the Cu(I) complexes. The influence of counteranions and pi-pi weak interactions on the formation and dimensionality of these coordination polymers has also been explored. In addition, the photoluminescence properties of Cu(I) coordination polymers 4-10 in the solid state have been studied.