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Three quinoline-based zinc(ii)–Schiff base complexes were synthesized and characterized by X-ray crystallography. They exhibit remarkable aggregation-induced emission enhancement (AIEE) in acetonitrile/diethyl ether mixtures due to the conversion of weak luminescence in homogeneous solution into strong emission in the nano-aggregated phase after increasing the fractions of diethyl ether. Interestingly, the AIEE performance can be significantly promoted by joining the two quinoline units through an alkoxy chain. Moreover, they show reversible mechanochromic luminescence behavior between dark and bright states during the grinding–fuming cycles, due to the modulation of morphologies between amorphous and crystalline states. Introducing an electron donating group in the para-position of aniline significantly improves the mechanochromic luminescence effect with a more accessible and distinct emission colour contrast. The molecular packing in the crystalline phase and time-dependent density functional theory (TD-DFT) calculations demonstrate that multiple intermolecular C–H…π and π–π interactions significantly strengthen the molecular rigidity and enhance the intramolecular charge-transfer (ICT) characteristics, leading to the effective emission enhancement in crystalline/nano-aggregated states. The novel AIEE and reversible mechanochromic luminescence properties point to the promising potential applications of these complexes in smart fluorescent materials. [ABSTRACT FROM AUTHOR]

We demonstrate a proof-of-concept design of a new platform for proton recognition and modulation. The new proton receptors are derived from a unique class of synthetic supercontainers that exhibit exceptional proton binding capacity (over 50 equiv.) and intriguing proton-dependent fluorescent switching behavior. Experimental and computational studies suggest that the proton-responsive event involves a two-step mechanism pertaining to proton binding by both amino and pyrenyl moieties of the supercontainer constructs. The high proton binding capacity of the supercontainers can be further modulated via small-molecule “regulators” that compete for the proton-binding sites, opening exiting new opportunities for proton manipulation in both chemistry and biology. [ABSTRACT FROM AUTHOR]

A new sulfonylcalix[4]arene-based dinuclear terbium molecular container (1) was conveniently synthesized and utilized as a fluorescence probe for the detection of a well-known biomarker 1-hydroxypyrene (1-OHP), which is used for the evaluation of polycyclic aromatic hydrocarbons (PAHs). The sulfonylcalix[4]arene ligand could not only serve as an efficient antenna ligand to promote the ligand-to-metal energy transfer but also provide a suitable cavity to accommodate 1-OHP. Promising fluorescence quenching effects were well established during the titration of the compound 1 with 1-OHP, and these effects were due to the enhancement in the host–guest intermolecular charge transfer and the decrease in the ligand-to-metal energy transfer after the formation of the stable host–guest complex. The fluorescence sensing mechanism was clearly understood through the titration experiments, and the data could be fit with the Benesi–Hildebrand and Stern–Volmer models. The TbIII-TBSC-based luminescent sensor exhibited quick response, high sensitivity, and specific selectivity to 1-OHP, even in the presence of other constituents in urine, thus providing a new sensing platform for the clinical diagnosis of human exposure to PAHs. [ABSTRACT FROM AUTHOR]

A series of Ag(i) and Cu(i) complexes [Ag3(L1)2][PF6]3 (8), [Ag3(L2)2][PF6]3 (9), [Cu(L1)][PF6] (10) and [Cu(L2)][PF6] (11) have been synthesized by reactions of the tridentate amine-bis(N-heterocyclic carbene) ligand precursors [H2L1][PF6]2 (6) and [H2L2][PF6]2 (7) with Ag2O and Cu2O, respectively. Complexes 10 and 11 can also be obtained by transmetalation of 8 and 9, respectively, with 3.0 equiv. of CuCl. A heterometallic Cu/Ag–NHC complex [Cu2Ag(L1)2(CH3CN)2][PF6]3 (12) is formed by the reaction of 8 with 2.0 equiv. of CuCl. All complexes have been characterized by NMR, electrospray ionization mass spectrometry (ESI-MS), and single-crystal X-ray diffraction studies. The luminescence properties of 10–12 in solution and the solid state have been studied. At room temperature, 10–12 exhibit evident luminescence in solution and the solid state. The emission wavelengths are found to be identical at 483 nm in CH3CN, but they are 484, 480 and 592 nm in the solid state for 10–12, respectively. These results suggest that 12 dissociates into two molecules of 10 and Ag(i) ions in solution. Complex 12 is the first luminescent heterometallic Cu/Ag–NHC complex. [ABSTRACT FROM AUTHOR]

4,5-Bis(2-methyl-5-phenylthiophen-3-yl)-1,3-dithiol-2-one (L1o) was elaborately designed to afford dithienyl-dithiolene as a new photochromic ligand. We describe herein the preparation and characterization of unprecedented photochromic dithienyl-dithiolene complexes with cis-orientation of dithienylethene (DTE) stabilized by metal chelation instead of conventional cyclopentene. The treatment of L1o with sodium methoxide in methanol afforded a disodium salt of dithiolate dianion, which reacts with M(dppe)Cl2 (dppe = 1,2-bis(diphenylphosphino)ethane, M = Ni, Pd) to give neutral compounds M(dppe)(dithiolate) as established by X-ray crystallography. The reaction of L1o with NiCl2 in the presence of sodium methoxide allows the isolation of an anionic nickel(ii) bis(dithienyl-dithiolene) complex with photochemical inertness. In contrast, the corresponding reaction with ZnCl2 afforded a dianionic zinc(ii) complex chelated by two dianionic dithienyl-dithiolenes, which displays stepwise photocyclization upon irradiation with UV light at 312 nm as demonstrated experimentally and theoretically. Only when dithienyl-dithiolene behaves as a dicationic ligand instead of neutral or monoanionic species, it is possible to achieve reversible photochromism in the corresponding metal complexes. [ABSTRACT FROM AUTHOR]

Cationic PtAu2 heterotrinuclear complexes [PtAu2(dpmp)2(C≡CR)2]2+ (dpmp = bis(diphenylphosphinomethyl)phenylphosphine, R = aryl) of aromatic acetylides were prepared. The PtAu2 structures are supported through doubly bridging dpmp and stabilized by a significant Pt–Au interaction. They are highly phosphorescent in fluid CH2Cl2 solution (Φem = 23.5%–78.9%), the solid state (Φem = 15.4%–70.2%), the PMMA film (Φem = 39.9%–71.7%) and the doping film of 61% TCTA : 31% OXD-7 : 8% PtAu2 complex (Φem = 16.9%–67.9%). The phosphorescence arises mainly from 3[π (C≡CR) →π* (dpmp)] 3LLCT and 3[π (C≡CR) → s/p (PtAu2)] 3LMCT triplet excited states for carbazole-acetylide complexes, whereas other complexes display a 3LLCT character mixed with noticeable PtAu2 centered 3[d → s/p] parentage. Utilizing a mixed host composed of hole-transporting TCTA and electron-transporting OXD-7 doped with 8% PtAu2 species as a light-emitting layer and CuSCN as a hole-transporting layer through an orthogonal solution process, the devices exhibit highly efficient electrophosphorescence with the highest current efficiency (CEmax) of 51.7 cd A−1 and external quantum efficiency (EQEmax) of 14.5%. The efficiency roll-off is small in the practical brightness range of 500–5000 cd m−2. The PtAu2 complexes with carbazole-acetylides display a higher electroluminescence efficiency ascribed to their better hole-transporting character as well as more facile energy transfer from mixed host materials. [ABSTRACT FROM AUTHOR]

Heterodimetallic Ru–Fe complexes [(tppz)(PPh3)2RuL](ClO4) (L = C≡CFc, [1](ClO4); C≡C–C6H4–C≡CFc), [2](ClO4); C≡C–C6H4–C6H4–C≡CFc, [3](ClO4)) were synthesized by the reactions of [(tppz)(PPh3)2RuCl](ClO4) (tppz = 2,3,5,6-tetrakis(2-pyridyl)pyrazine) with ferrocence-acetylide ligands and characterized by ESI-MS, and 1H and 31P NMR spectroscopies. The structure of [1](PF6) was determined by X-ray crystallography. The electrochemical studies show that compounds [1](ClO4)–[3](ClO4) possess two widely separated anodic peaks, ascribable to one-electron oxidation of Fc and RuII, respectively. This assignment is further corroborated by the results of UV-vis-NIR, XPS, and theoretical calculation studies. Compound [1](ClO4) exhibits significant Ru…Fe metal–metal interactions across the Ru–C≡C–Fc backbone. As revealed by electrochemical, spectroscopic and theoretical computational studies, one-electron oxidized species [1a](ClO4)2 is between the electronically delocalized and valence-trapped state and shows a typical Robin–Day class II mixed-valence behavior. [ABSTRACT FROM AUTHOR]

We have synthesized four Ir(iii) metal complexes (1–4) bearing dual fluorine-free cyclometalates that are derived from 2′,6′-dimethoxy-4-t-butyl-2,3′-bipyridine (pypy)H or 2-(2,4-dimethoxypyrimidin-5-yl)-4-t-butylpyridine (pmpy)H and a third ancillary, e.g. 5-pyridin-2-yl-pyrazolate (Pz) or 5-pyridin-2-yl-pyrrolide (Pr), respectively. The Ir(iii) complexes 3 and 4 were examined by X-ray diffraction studies for providing the structural proofs. Photophysical properties were next measured in CH2Cl2 at RT, among which the pypy complexes 1 and 2 showed an identical structured emission with an E0-0 peak located at 458 nm, while the corresponding pmpy derivative 3 displayed the most blue-shifted E0-0 peak at 444 nm. Organic light-emitting diodes (OLEDs) were fabricated using multiple layered architecture and the aforementioned phosphor at 8 wt% doping level. The associated OLED performances, cf. max. E.Q.E. = 9.0%, 14.3%, 5.8% and 9.4% and CIEx,y coordinates at (0.16, 0.22), (0.16, 0.24), (0.16, 0.17) and (0.16, 0.20) at 100 cd m−2 for phosphors 1–4 in sequence, confirmed their potential to act as blue dopants for phosphorescent OLEDs. [ABSTRACT FROM AUTHOR]

The planar platinum(ii) complex [Pt(Me3SiC≡CbpyC≡CSiMe3)(C≡CC6H4Et-4)2] (1) with 5,5-bis(trimethylsilylethynyl)-2,2′-bipyridine was prepared and characterized. Solid-state 1 exhibits unusual, selective and reversible luminescence vapochromism to CH3CN and ClCH2CN vapors, which is useful for the detection of these hazardous vapors. A vapochromic cycle was monitored by dynamic variations in emission spectra and X-ray diffraction (XRD) patterns. Both X-ray crystallographic and density functional theory studies suggest that the vapochromic and vapoluminescent behavior of 1 are induced by the variation in the intermolecular Pt–Pt interactions. [ABSTRACT FROM AUTHOR]

A series of platinum(ii) complexes with 1,3-bis(2-pyridylimino)isoindoline (BPI) derivatives were prepared by substitution of the coordinated Cl in the precursor complex Pt(BPI)Cl with a N-heterocyclic ligand such as pyridine, phthalazine or phenanthridine. These complexes display orange to red luminescence in fluid dichloromethane solutions and in the solid states at room temperature. The photophysical properties were tuned by introducing electron-withdrawing -NO2or electron-donating -NH2to the BPI ligand. The DFT computational studies suggest that the emission in the N-heterocyclic ligand substituted platinum(ii) complexes originates mainly from the 3[π→π*(BPI)] 3IL triplet excited state, mixed with some 3[dπ(Pt)→π*(BPI)] 3MLCT character. Compared with the precursor Pt(BPI)Cl, both the low-energy absorption and the emission in the N-heterocyclic ligand substituted platinum(ii) complexes exhibits a distinct blue-shift due to an obviously enhanced contribution from the 3IL state and a reduced 3MLCT character. [ABSTRACT FROM AUTHOR]

Three new dinuclear lanthanide(iii) complexes {Eu(hfac)3(H2O)}2(μ-HPhMq)2(2) and {Ln(hfac)3(H2O)}2(μ-HMe2NC6H4Mq)2(Ln = Eu, 3; Nd, 4) with 8-hydroxylquinoline derivatives in μ-phenol mode were synthesized and characterized, where hfac−= hexafluoroacetylacetonate, HPhMq = 2-methyl-5-phenylquinolin-8-ol, and HMe2C6H4Mq = 5-(4-(dimethylamino)phenyl)-2-methylquinolin-8-ol. Compared with that (400 nm) for {Eu(hfac)3}2(μ-HMq)2(1, HMq = 2-methy-8-hydroxylquinoline), the excitation wavelength for sensitized lanthanide luminescence is extended to ca.420 nm for 2, and 500 nm for 4by introducing a phenyl or 4-(dimethylamino)phenyl to 8-hydroxylquinoline. These dinuclear lanthanide(iii) complexes exhibit distinctly fluoride-induced lanthanide(iii) emission enhancement in both intensity and lifetime due to replacing coordination water molecules or formation of strong O–HF hydrogen bonds with coordinated H2O and μ-phenol, thus suppressing significantly the non-radiative O–H oscillators. [ABSTRACT FROM AUTHOR]

A new Cu2+-responsive MRI contrast agent (Gd-QDOTAMA) with a quinoline-based ligand was synthesized and characterized. Relaxivity studies on Gd-QDOTAMA showed that the relaxivity increased from 4.27 mM−1s−1to 7.29 mM−1s−1in response to equimolar amounts of copper(II) ion, corresponding to ca.71% relaxivity enhancement. Distinct changes in relaxivity were undetected upon addition of physiologically relevant alkali metal cations (K+or Na+), alkaline earth metal cations (Mg2+or Ca2+), or d-block metal cations (Zn2+, Cu+, Fe2+, Fe3+), indicating a high selectivity for Cu2+over other biologically relevant metal ions. Moreover, the influence of common biological anions at physiological levels on the Cu2+-responsive contrast agent was also studied. Luminescence studies on the Eu counterpart Eu-QDOTAMA suggest that the enhancement in relaxivity for Gd-QDOTAMA in response to Cu2+is most likely due to the increased number of inner-sphere water molecules around Gd3+upon Cu2+binding to the 8-amidequinoline moiety. In vitroT1-weighted phantom images of Gd-QDOTAMA confirmed that signal intensity was markedly increased by the addition of equimolar amounts of Cu2+. [ABSTRACT FROM AUTHOR]

An iridium(iii)-containing phosphorescent chemosensor Ir(ppy)2(L)(PF6) (1, ppy = 2-phenylpyridine) containing a 2,2′-bipyridyl ligand (L) functionalized with an α,β-unsaturated ketone for selective detection of thiol was synthesized and characterized by spectroscopic and photophysical measurements. The structure of complex 1was determined by X-ray crystallography. In order to get an insight into 1,4-addition reactions of thiol to complex 1, the adduct 2from reaction of 1with benzenethiol was successfully prepared and characterized. Complex 1shows a lowest energy absorption at ca.450 nm, primarily ascribable to an intraligand charge transfer (ILCT) transition from the HOMO (π) resident on the fragment -C(O)C6H4N(C2H5)2to the LUMO (π*) localized on the 2,2′-bipyridyl moiety in the functionalized 2,2′-bipyridyl ligand as suggested from DFT computational studies. Complex 1is weakly emissive at ca.587 nm at ambient temperature, arising likely from the 3ILCT excited state. Upon addition of thiol to a semi-aqueous solution of complex 1, the lowest energy absorption is obviously blue-shifted and the emission is remarkably enhanced due probably to a conversion from the primary ILCT state to the predominant [π(ppy)→π*(L)] LLCT and the [5d(Ir)→π*(L)] MLCT state caused by the formation of the 1-thiol adduct. The sensing properties of 1to thiol were also investigated by ESI-MS spectrometry and 1H NMR spectroscopy. [ABSTRACT FROM AUTHOR]

A series of oxo-centred triruthenium-acetate complexes with valence iii,iii,iiwere prepared by reactions of [Ru3III,III,III]+precursor [Ru3O(OAc)6(py)2(CH3OH)]+(1) with 3-chloro-6-(pyrazol-1-yl)pyridazine (cppd), 3-chloro-6-(3,5-dimethylpyrazol-1-yl)pyridazine (cmppd), 3,6-bis(pyrazol-1-yl)pyridazine (ppd), 3,6-bis(3,5-dimethylpyrazol-1-yl)pyridazine (mppd) or 3,6-bis(2-pyridyl)-1,2,4,5-tetrazine (bptz). When neutral Ru3III,III,IIprecursor Ru3O(OAc)6(CO)(CH3OH)2(2) was utilized, a stable low-valence Ru3III,II,IIderivative complex was successfully isolated. As established through crystal structural analyses, they were derived from 1or 2by substitution of the axial methanol and one of six bridging acetates in the parent Ru3(μ3-O)(μ-OAc)6cluster core as well as one axial pyridine in some cases. As revealed by electrochemical and spectroscopic studies, substituting one of the six bridging acetates in the parent Ru3(μ3-O)(μ-OAc)6cluster core significantly modifies the electronic and redox characteristics. Compared with those for the parent compound [Ru3O(OAc)6(py)3]+, triruthenium-based redox potentials of these derivatives show remarkable positive shifts. [ABSTRACT FROM AUTHOR]