A trinuclear heterobimetallic Ru(II)/Pt(II) complex as a chemodosimeter selective for sulfhydryl-containing amino acids and peptides

A trinuclear heterobimetallic Ru(II)/Pt(II) complex, cis-{Ru(phen)2[CN-Pt(DMSO)Cl2]2} (phen = 1,10-phenanthroline), is able to function as a "switch-on" luminescent chemodosimeter for sulfhydryl-containing amino acids and peptides via specific binding of the amino acids/peptides with the Pt(II) centers and the subsequent cleavage of the Ru(II)-Pt(II) cyano-bridge.     

Catalytic Chemosensing Assay for Selective Detection of Methyl Parathion Organophosphate Pesticide

Herein, a catalytic chemosensing assay (CCA), based on a bimetallic complex, [Ru^II(bpy)₂(CN)₂]₂(Cu^II)₂ (bpy=2,2′-bipyridine), is described. This complex integrates a task-specific catalyst (Cu^I-catalyst) and a signaling unit ([Ru^II(bpy)₂(CN)₂]) to specifically hydrolyze methyl parathion, a highly toxic organophosphate (OP) pesticide. The bimetallic complex catalyzed the hydrolysis of the phosphate ester to generate o,o-dimethyl thiophosphate (DTP) anion and 4-nitrophenolate. Intrinsically, 4-nitrophenolate absorbed UV/Vis light at λ_max=400 nm, creating the first level of the chemosensing signal. DTP interacted with the original complex to displace the chromophore, [Ru^II(bpy)₂(CN)₂], which was monitored by spectrofluorometry; this was classified as the second level of chemosensing signal. By integrating both spectroscopic and spectrofluorometric signals with a simple AND logic gate, only methyl parathion was able to provide a positive response. Other aromatic and aliphatic OP pesticides (diazinon, fenthion, meviphos, terbufos, and phosalone) and 4-nitrophenyl acetate provided negative responses. Furthermore, owing to the metal-catalyzed hydrolysis of methyl parathion, the CCA system led to the detoxification of the pesticide. The CCA system also demonstrated its catalytic chemosensing properties in the detection of methyl parathion in real samples, including tap water, river water, and underground water.     

Crystallization-driven constitutional changes of dynamic polymers in response to neat/solution conditions

Dynamic polymers (dynamers) based on reversible imine interactions were generated and found to respond to changes in neat/solution environment, thus displaying adaptive behavior through modification of their constitution in order to maximize the stability of their mesoscopic state as a function of conditions.     

Design and synthesis of heterobimetallic donor-acceptor chemodosimetric ensembles for the detection of sulfhydryl-containing amino acids and peptides

A competitive indicator displacement assay has been successfully developed for the ratiometric determination of sulfhydryl-containing amino acids and peptides using heterobimetallic donor-acceptor complexes as chemodosimetric ensembles. Chromotropic cis-[ML2(CN)2](M = FeII, RuII, OsII; L = diimine) are used as signaling indicators and PtII(DMSO)Cl2 acceptor moiety is used as the receptor for the sulfhydryl-containing analytes. A series of three heterobimetallic donor-acceptor complexes: cis-FeII(bpy)2[CN-PtII(DMSO)Cl2]2 (1), cis-Ru(II)(bpy)2[CN-PtII(DMSO)Cl2]2 (2) and cis-Os(II)(bpy)2[CN-PtII(DMSO)Cl2]2 (3) are synthesized and characterized by X-ray crystallography. All the three ensembles are able to produce specific colorimetric/fluorimetric responses to sulfhydryl-containing amino acids (cysteine, homocysteine and methionine) as well as the sulfhydryl-containing small peptide glutathione. The mechanism of the competitive displacement assay is evaluated by examining the thermodynamics of formation of the donor-acceptor linkage and adducts between the acceptor metal and the sulfhydryl-containing analytes as well as by systematic variation of the donor and acceptor metals in the chemodosimetric ensembles.     

Novel Iron-Based Polynuclear Metal Complexes [FeII(L)(CN)4]2–[FeIII(H2O)3Cl]2: Synthesis and Study of Photovoltaic Properties for Dye-Sensitized Solar Cell

A series of novel polynuclear iron-based photosensitizers (1–3) with cyano-bridged to form a molecular square were synthesized and their optical, electrochemical, and photovoltaic properties were investigated. The modification of anchoring groups with 4,4'-dicarboxy-2,2'-bipyridine, 2,2'-bipyridine, and 4,4'-dimethoxy-2,2'-bipyridine does not show significant changes on the both absorption and electrochemical properties of these iron-based dyes. This indicates that the polynuclear iron-based photosensitizers have better flexibility to regulate their physical properties of solubility, surface absorption, and thin-film formation for device preparation. The polynuclear new dyes show power conversion efficiencies ranged from 0.43 to 0.48% that is almost the best system among the published iron-based photosensitizers. These iron-based dyes were able to chemisorb on TiO₂ surface efficiently and then promoting electron injection and photocurrent generation in a dye-sensitized solar cell with solar irradiation.

     

Supramolecular Polymeric Chemosensor for Biomedical Applications: Design and Synthesis of a Luminescent Zinc Metallopolymer as a Chemosensor for Adenine Detection

Adenine is an important bio-molecule that plays many crucial roles in food safety and biomedical diagnostics. Differentiating adenine from a mixture of adenosine and other nucleic bases (guanine, thymine, cytosine, and uracil) is particularly important for both biological and clinical applications. A neutral Zn^II metallosupramolecular polymer based on acyl hydrazone derived coordination centres (P1) were generated through self-assembly polymerization. It is a linear coordination polymer that behaves like self-standing film. The synthesis, ¹H-NMR characterization, and spectroscopic properties of this supramolecular material are reported. P1 was found to be a chemosensor specific to adenine, with a luminescent enhancement. The binding properties of P1 with common nucleic bases and nucleosides reveal that this supramolecular polymer is very selective to adenine molecules (~20 to 420 times more selectivity than other nucleic bases). The formation constant (K) of P1 to adenine was found to be log K?=?4.10?±?0.02. This polymeric chemosensor produces a specific response to adenine down to 90?ppb. Spectrofluorimetric and ¹H-NMR titration studies showed that the P1 polymer allows each Zn^II coordination centre to bind to two adenine molecules through hydrogen bonding with their imine and hydrazone protons.     

Synthesis and spectroscopic studies of cyclometalated Pt(II) complexes containing a functionalized cyclometalating ligand, 2-phenyl-6-(1H-pyrazol-3-yl)-pyridine

Three new luminescent cyclometalated Pt(II) complexes, [Pt(L)Cl] (1), [Pt2(L-)2] (2), and [Pt(L)(PPh3)]ClO4 (3.ClO4) (where HL=2-phenyl-6-(1H-pyrazol-3-yl)-pyridine), were synthesized and characterized by X-ray crystallography. HL represents a new class of C,N,Npyrazolyl cyclometalating ligands containing a Cphenyl, a Npyridyl, and a Npyrazolyl donor moiety, as well as a 1-pyrazolyl-NH, that can also be available for metal coordination and other chemical interactions. Complex 1 possesses intense intraligand transitions at 275-375 nm and moderately intense metal-to-ligand charge transfer (1MLCT) (dpi(Pt)-->pi*(L)) transition at 380-410 nm. The room temperature solid-state emission lambdamax of 1 occurs at 580 nm and is attributable to the 3MMLCT (dsigma*(Pt)-->pi*(L)) transition. It also displays strong phosphorescence in acetonitrile solutions at room temperature with an emission lambdamax at 514 nm, which can be tentatively assigned to the 3MLCT (pi*(L)-->dpi(Pt)) transition. Complex 1 can be deprotonated in organic solvents to yield a cycloplatinated dimer 2, which shows a relatively high room-temperature luminescent quantum yield of 0.59 in DMF (lambdamax=509 nm). Substitution of the ancillary chloro-ligand in 1 by triphenylphosphine yields 3, which also possesses a good room-temperature luminescent quantum yield of 0.52 in DMF (lambdamax=504 nm) and a better solubility in water. Complex 3 is synthesized to demonstrate the pH dependence of luminescent properties of this C,N,Npyrazolyl cyclometalated Pt(II) system. Such a pH response is ascribable to the protonation/deprotonation of the 1-pyrazolyl-NH on the C,N,Npyrazolyl cyclometalating ligand. The pKa of the 1-pyrazolyl-NH in 3, measured in 1:2 (v/v) aqueous DMF solutions, is approximately 4.0.     

The synthesis and photophysical studies of cyclometalated Pt(II) complexes with C,N,N-ligands containing imidazolyl donors

Two new C,N,N-type ligands (HL(2) and HL(3)), containing a C(phenyl), a N(pyridyl), and a N(imidazolyl) donor, and their cycloplatinated complexes, [Pt(L(2))Cl] (1), [Pt(L(3))Cl] (2), [Pt(L(2))(PPh(3))](+) (3) and [Pt(L(3))(PPh(3))](+) (4), have been successfully synthesized and characterized. Spectroscopic and (3)MLCT luminescent properties of these Pt(II) cyclometalated complexes were found to be pH dependent. This was attributed to the protonation/deprotonation of the acidic 1-imidazolyl-NH moieties on the ligands. All the cycloplatinated complexes (both protonated and deprotonated forms) possessed two-photon excitability with two-photon absorption cross-sections ranging from 6.0 to 30.0 GM (protonated forms) and from 16.2 to 24.9 GM (deprotonated forms).