Luminescent Cu(Ⅰ) and Ag(Ⅰ) coordination polymers:Fast phosphorescence or thermally activated delayed fluorescence

By applying two donor-acceptor motif molecules,5,10-di(pyridin-4-yl)-5,10-dihydrophenazine(LI)and 10,10'-di(pyridin-3-yl)-10 H,10'H-9,9'-spiroacridine(L2),as ligands and CuI/AgCF_3 CO_2 as metal salt,we synthesized three coordination polymers,namely,{Cu_4(L1)_2 I_4}(CP1),{Cu(L2)I-CHCl_3}(CP2) and{Ag(L2)CO_2 CF_3·CHCl_3}(CP3).X-ray crystallographic analysis revealed that three coordination polymers all feature one-dimensional(1 D) linear chains which are consisting of molecular boxlike units.In comparison with low photoluminescence quantum yield(PLQY) of two ligands,three coordination polymers.CP1,CP2 and CP3,present more intense photoluminescence with PLQY of 15%,46% and 34% at room temperature respectively.The PL emission of CP1 and CP2 at room temperature could be attributed to the fast phosphorescence with lifetime both around 5 μs due to effective intersystem crossing(ISC).Whilst,it is worth noting that CP3 exhibit thermally activated delayed fluorescence(TADF) emission at room temperature.     

Synthesis,aggregation-induced emission and thermally activated delayed fluorescence properties of two new compounds based on phenylethene,carbazole and 9,9′,10,10′-tetraoxidethianthrene

In the text, two luminescent materials ECPPTT and ECDPTT, have been designed and synthesized by integrating tetraphenyl/triphenyl-ethene(TPE/TrPE), carbazole group and thianthrene-9,9,10,10-tetraoxide unit. ECPPTT and ECDPTT possess obvious AIE and TADF capabilities, and show good thermal stability in their thin film of 240 °C and 262 °C, respectively. Non-doped organic light emitting diodes(OLED) using ECPPTT and ECDPTT as emission layer are prepared and exhibit blue-green and green emission color with peaks at 494, 517 nm, respectively. The non-doped OLED based on ECPPTT provides good peak EL efficiencies of 3.437 cdA^-1 and 10090cdm^-2; while non-doped OLED fabricated with ECDPTT affords a maximum current efficiency and a maximum luminance of 2.478 cdA^-1 and 7561cdm^-2. These results have demonstrated the feasibility of combing AIE and TADF units to design new molecules.     

Modulation of luminescence by subtle anion-cation and anion-π interactions in a trigonal Au(I)···Cu(I) complex

The trigonally coordinated [AuCu(PPh(2)py)(3)](BF(4))(2) (1) crystallizes in two polymorphs and a pseudopolymorph, each of which contains a trigonally coordinated cation with short Au(I)-Cu(I) separations of ～2.7 ?. Under UV illumination, these crystals luminesce different colors ranging from blue to yellow. The structures of these cations are nearly superimposable, and the primary difference resides in the relative placement of the anions and solvate molecules. As confirmed by time-dependent density functional theory calculations, it is these interactions that are responsible for the differential emission properties.     

Theoretical studies on the mechanism of the thermal decarboxylation and decarbonylation of a number of α-keto-acids

Both processes of decarboxylation and decarbonylation of a number of acids including RCOCO2H,R=H,CH3,CH2F,CF3,CH=CH2,Ph,OH have been studied by semi-empirical MO theory AMI method to verify the reaction mechanism of each process and the effect of different substituents on them.The calculated results are consistent with the experimental reports and can be summed up as follows:(1) The decarboxylation of these acids to form aldehydes and carbon dioxide is concerted and takes place through a 4-membered ring transition state in which a partial negative charge develops on the carbon of the α-carbonyl group,so that the inductive effect of some substituents is favourable for this process.(2) Their decarbonylation into carboxylic acids and carbon monoxide however is the attack of the OH on the carbon of the alkyl portion of the acid,forming a 3-membered ring transition state.(3) The activation energy of decarbonylation is lower than that of decarboxylation,since oxygen is more nucleophilic than hydrogen and als     

Theoretical studies on electronic structures and spectroscopic properties of a series of novel β-diketonate Os(II) complexes

The geometries, electronic structures, and spectroscopic properties of a series of [Os^(II)(CO)₃(tfa)(acac(X)₂)] (tfa = trifluoroacetate; acac = acetoylacetonate; X = H (1), CF₃ (2), C₆H₅ (3), and C₁₀H₇ (4)) complexes have been investigated theoretically. The ground and excited state geometries were optimized at the B3LYP/LANL2DZ and CIS/LANL2DZ levels, respectively. The optimized geometry structural parameters agreed well with the corresponding experimental results. As indicated in this paper, the highest occupied molecular orbitals were dominantly localized on the Os atom, ctfa (abbv. of CO and tfa), and acac ligand for 1 and 2, acac ligand and X substituent for 3 and 4, while the lowest unoccupied molecular orbitals were mainly composed of acac ligand and X substituent. Under the time-dependent density functional theory (TDDFT) level with the polarized continuum model (PCM), the absorption and phosphorescence in CH₂Cl₂ media were calculated based on the optimized ground- and excited-state geometries, respectively. The calculated results show that the lowest energy absorptions at 317 (1), 342 (2), 377 (3), and 420 nm (4) are attributed to a change of ππ*/MLCT mixing transition to pure ππ* transition for 1–4, while their phosphorescence emission have similar transition properties. This indicates that the absorption and emission transition characters could be altered by adjusting the π electron-donating ability.     

Hydrothermal synthesis,structure and properties of a heteronuclear Co(III)–Ag(I) complex with the 2,6-pyridine-dicarboxlate

A new Ag/Co coordination polymer, [AgCo(PDC)₂] (1) (H₂PDC?=?2,6-pyridine-dicarboxylic acid) was synthesized under hydrothermal condition. X-ray crystallographic study reveals that 1 is a 2D network and has a previously unexplored coordination mode. Solid state fluorescence and thermogravimetric analysis (TGA) have been performed.     

Theoretical studies on cation-π interactions (I)——Density-functional theory investigation on the configurations and interaction for ammonium cation-benzene complex

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Theoretical studies on the spectroscopic properties and the substituent effects of pyridyl triazole Os(Ⅱ) complexes

To explore the spectroscopic properties of pyridyl triazole Os(Ⅱ) complexes and how the substituent effects affect the spectroscopic properties of [Os(ptz)2L2] (L=PH3; ptzH=(2-pyridyl)-1,2,4-triazole) (1), [Os(bptz)2L2] (bptzH=3-tert-butyl-5-(2-pyridyl)-1,2,4-triazole) (2), [Os(fptz)2L2] (fptzH=3- (trifluoreomethyl)- 5-(2-pyridyl)-1,2,4-triazole) (3), and [Os(fbtz)2L2] (fbtzH=3-(trifluoreomethyl)-5-(4-tert-butyl- 2-pyridyl)-1,2, 4-triazole) (4), the density functional theory (DFT) method at the B3LYP level ...     

Theoretical studies on structures and UV-Vis spectra of C_(70)O

Systematic studies on eight isomers of C70O were performed by means of INDO methods It has been indicated that the O atom is mainly added to the C1-C2 or C3-C3 bond and an epoxide feature with C1 symmetry is formed.Based on the optimized geometries,the UV-Vis spectra were calculated.It has been found that the main peaks of C70O resemble those of C70 and the characteristic absorptions beyond 460 nm are produced,which is m agree ment with the experimental results.Theoretical assignments about the absorptions were carried out and the reason for the red-shift of the absorptions was discussed.C70O is probably composed of four isomers according to the calculated results.     

Structural,spectroscopic, luminescence sensing and TD–DFT theoretical studies of a CuP2N-type complex

Luminescent cuprous complexes are an important class of coordination compounds due to their relative abundance, low cost and ability to display excellent luminescence. The title heteroleptic cuprous complex, [2,2′-bis(diphenylphosphanyl)-1,1′-binaphthyl-κ²P,P′](2-phenylpyridine-κN)copper(I) hexafluoridophosphate, rac-[Cu(C₄₄H₃₂P₂)(C₁₁H₉N)]PF₆, conventionally abbreviated rac-[Cu(BINAP)(2-PhPy)]PF₆ ( I ), where BINAP and 2-PhPy represent 2,2′-bis(diphenylphosphanyl)-1,1′-binaphthyl and 2-phenylpyridine, respectively, is described. In this complex, the asymmetric unit consists of a hexafluoridophosphate anion and a heteroleptic cuprous complex cation, in which the cuprous centre in a CuP₂N coordination triangle is coordinated by two P atoms from the BINAP ligand and by one N atom from the 2-PhPy ligand. Time-dependent density functional theory (TD–DFT) calculations show that the UV–Vis absorption of I should be attributed to ligand-to-ligand charge transfer (LLCT) characteristic excited states. It was also found that the paper-based film of this complex exhibited obvious luminescence light-up sensing for pyridine.     

Aggregation-induced phosphorescence and mechanochromic luminescence of a tetraphenylethene-based gold(Ⅰ) isocyanide complex

In this study,a new twisting gold(Ⅰ) isocyanide complex based on tetraphenylethene(TPE),TPE-NC-Au.was designed and synthesized.It exhibits aggregation induced phosphorescence(AIP) characteristics,owing to the incorporation of Au moiety and conformation rigidification in the aggregated states.Moreover,the emission color of the crystalline solid of TPE-NC-Au changes from blue(454 nm) to green(500 nm) in response to mechanical grinding,due to the combined effects of conformation planarization,enhanced π…π stacking,as well as the emergence of aurophilic interactions in the ground amorphous state.Notably,the emission color can be restored upon solvent fuming,associating with the reconstruction of crystalline lattices.The AIP and switchable mechanochromism of TPE-NC-Au make it suitable for potential applications in bioimaging,sensing,and optoelectronic devices.     

Synthesis and properties of a functionalized heterobimetallic Re(I)–Gd(III) complex as a potential dual-contrast agent for molecular imaging

In the design of dual-imaging probes, the first functionalized and neutral heterobimetallic Re(I)–Gd(III) complex, highly soluble in aqueous solutions, has been prepared. This system exhibits interesting photophysical properties (λ_em = 578 nm, ? = 1.4%) for optical imaging and substantial higher relaxivity (r₁ = 6.6 mM⁻¹ s⁻¹ at 0.47 T and 37 °C) than the clinically used MRI contrast agents. Moreover, this system incorporates an aromatic ester functionality suitable for bioconjugation.     

Synthesis,characterization and antibacterial activity of a curcumin–silver(I) complex

The current study reports the synthesis of a curcumin–silver(I) complex and its preliminary tests against four bacterial strains viz. Staphylococcus aureus, Escherichia coli, Bacillus subtilis, and Bacillus cereus using agar well diffusion method. The results were compared with curcumin by testing it in parallel with the sample. Curcumin showed zones of inhibition against all tested strains of bacteria. Among all bacterial strains, S. aureus was the most sensitive to curcumin with zone of inhibition of 12.2 mm. However, the curcumin–Ag(I) complex did not show the expected enhanced activity against all bacteria. This is perhaps due to the replacement of curcumin phenolic protons by silver ions which might have suppressed the antibacterial property of curcumin. The current research findings suggest that while synthesizing curcumin–metal complexes, the phenolic heads may either be left unaltered or need to be replaced by better substituents than hydroxy groups. Based on the current findings, biologically enhanced models have been provided as future recommendations.     

Theoretical study on the reaction mechanism of NH2(-) with O2 (a1Δg)

A detailed theoretical study of the potential energy surface of poorly understood ion-molecule reaction of NH(2)(-) and O(2) (a(1)Δ(g)) is explored at the density functional theory B3LYP/6-311++G(d,p), ab initio of QCISD/6-311++G(d,p) and CCSD(T)/6-311++G(3df, 2pd) (single-point) theoretical levels for the first time. It is shown that there are six total possible products from P(1) to P(6) on the singlet potential energy surface. Among these, the charge-transfer product P(1) (NH(2) + O(2)(-)) is the most favorable product with predominant abundances, whereas P(4) (NO(-) + H(2)O) and P(2) (HNO + OH(-)) may be the second and third feasible products followed by the almost neglectable P(3) (NO(2)(-) + H(2)), while P(5) (c-NO(2)(-) + H(2)) and P(6) (ONO(-) + H(2)) will not be observed due to their either high barriers or being secondary products. The present theoretical study points out that besides P(1) (NH(2) + O(2)(-)) and P(2) (HNO + OH(-)), P(4) (NO(-) + H(2)O) should be also observed, which is different from the previous experiment study by Anthony Midey et al. in 2008. In addition, almost all of the reaction pathways to products are exothermic and the reaction rate should be very fast since the reaction barriers are very low except for P(5) (c-NO(2)(-) + H(2)) which is in agreement with the measured total reaction rate constant k = 9.0 × 10(-10) cm(3)s(-1) at 300 K in the experiment study. It is expected that the present theoretical study may be helpful for the understanding of the reaction mechanism related to NHX(-), NX(2)(-), PHX(-), and PX(2)(-) (X = H, F, and Cl).     

Spectroscopic (fluorescence, 1D-ROESY) and theoretical studies of the thiabendazole and β-cyclodextrin inclusion complex

The inclusion complex between the anti-helminthic drug thiabendazole (TBZ) and the β-cyclodextrin (βCD) was characterized in solution using fluorescence and ¹H-Nuclear Magnetic Resonance spectroscopy and studied theoretically by semi empirical PM3 and density functional theory (DFT) quantum mechanical calculations. Thermodynamic stability associated with the formation of the TBZ:βCD inclusion complex in aqueous solution was determined treating the drug’s fluorescence enhancement in the presence of cyclodextrin by a non-linear model, which indicated a moderate host–guest affinity at equilibrium (K 150 ± 31 at 25 °C). Its supramolecular structure in solution was studied through the 1D-ROESY NMR experiment, which produced evidence that the guest molecular encapsulation occurs preferably via the drug’s benzimidazole group. Theoretical study employing molecular optimization with the semi empirical PM3 method provided two energetic-equivalent complex structures that are in accordance with the NMR experimental evidences. Single point energy calculations with DFT at the B3LYP/6-31G (d,p) level suggest the most stable structure of the inclusion complex and further comprehension on the interactions and conformational strains involved in its formation.     

Synthesis,characterization and luminescence properties of a coordination polymer based on self-assembly of PrIII with inorganic–organic hybrid bridging ligands

A new coordination polymer having the formula [Pr(μ ₅-S₂O₃)(μ ₄-tp)_0.5(H₂O)] _n (1) (S₂O₃ = thiosulfate dianion; tp = terephthalate dianions) was obtained by in situ reaction of Pr₂(SO₄)₃ · 6H₂O with H₂tp ligands under solvothermal conditions (H₂O/ethanol). The coordination polymer obtained was characterized by elemental analysis, FT-IR, thermogravimetry (TG), fluorescent spectra and single crystal X-ray diffraction analysis. The most intriguing structural feature is that the complex exhibits a 3D open framework resulting from bridge-linking coordination between ligands and praseodymium ions. Additionally, 1 has characteristic emission spectra of Pr^III with good fluorescence properties. This is the first coordination polymer based on thiosulfate/terephthalate ligands and a rare earth metal and has an unprecedented pentadentate-bridge-linking coordination mode of the thiosulfate group.     

Review: Multimetallic silver(I)–pyridinyl complexes: coordination of silver(I) and luminescence

This review highlights some structural features and luminescent properties of homo- and hetero-multinuclear silver(I)–pyridinyl complexes. It focuses on the coordination and geometry of the silver(I) ions to the pyridinyl-nitrogen. For this reason, we have considered only pyridinyl-N–Ag(I) complexes whose crystal data are available. In addition, this review does not consider mononuclear silver(I)–pyridinyl complexes as these have been reviewed elsewhere. This is motivated by the fact that multinuclear silver(I)–pyridinyl complexes have been shown to be more stable in solution, possess enhanced properties, and have fascinating structures compared to their mononuclear counterparts. The introduction highlights pyridinyl ligands used in complexation of silver(I) ions. The main body highlights complexation of silver(I) through pyridinyl nitrogen and the interactions found in the multinuclear silver(I)–pyridinyl complexes as well as the coordination number and geometry of silver(I) centers. Though silver(I) has been flaunted to prefer linear twofold coordination geometry, from this review, it is clear that higher coordination numbers in varied geometries are possible. These include distorted trigonal planar, T-shaped, distorted tetrahedral, trigonal bipyramidal, and octahedral geometries. Coordination of silver(I) to pyridinyl ligands and their metalloligands has been observed to impart or enhance luminescent properties in the ensuing complexes.     

Pre-concentration and quantification of aluminum in fish samples using a dispersive liquid–liquid micro-extraction–spectrofluorimetric method based on Al(III)–8-hydroxyquinoline complex’s fluorescence properties

A simple and fast dispersive liquid–liquid micro-extraction (DLLME)–spectrofluorimetric technique was developed and validated for the extraction and quantification of trace amounts of Al in fish samples, where 8-hydroxyquinoline was utilized as a spectrofluorimetric probe. In order to optimize the efficacy of the DLLME technique, the impact of experimental parameters on the extraction of Al(III) from fish samples was evaluated. Under the optimal conditions, the method was linear in the concentration range of 0.1–7.0 μg/g (r = 0.9996) with a LOD of 0.092 μg/g; additionally, the method was accurate (RE% of ? 3.0 to + 10.0%), precise (RSD% of 1.2–14.3%) and robust (RSD% of 3.8 and p value of 0.21) and its recovery was in the range of 97.0 ± 3.89–110.0 ± 12.5%; moreover, samples were stable before and during the analyses. Therefore, it can be claimed that the developed method could be successfully applied for the quantification of Al in fish samples.     

Electrochemical and STM studies of 1-thio-β-D-glucose self-assembled on a Au(111) electrode surface

In this study, a Au(111) electrode is functionalized with a monolayer of 1-thio-β-D-glucose (β-Tg), producing a hydrophilic surface. A monolayer of β-Tg was formed on a Au(111) surface by either (1) potential-assisted deposition with the thiol in a supporting electrolyte or (2) passive incubation of a gold substrate in a thiol-containing solution. For each method, the properties of the β-Tg monolayer were investigated using cyclic voltammetry (CV), differential capacitance (DC), and chronocoulometry. In addition, electrochemical scanning tunneling microscopy (EC-STM) was used to obtain images of the self-assembled monolayer with molecular resolution. Potential-assisted assembly of β-Tg onto a Au(111) electrode surface was found to be complicated by oxidation of β-Tg molecules. The EC-STM images revealed formation of a passive layer containing honeycomb-like domains characteristic of a formation of S(8) rings, indicating the S-C bond may have been cleaved. In contrast, passive self-assembly of thioglucose from a methanol solution was found to produce a stable, disordered monolayer of β-Tg. Since the passive assembly method was not complicated by the presence of a faradaic process, it is the method of choice for modifying the gold surface with a hydrophilic monolayer.