Preparation and photophysical properties of precursors of inorganic macromolecules. Mono and binuclear complexes of Ru(II) and terpyridine derivatized with thiophene and 4-(5-bromothiophene) groups

The preparation and characterization of mono and binuclear complexes of Ru(II) with a newly synthesized derivate of the terpyridine ligand, 4^′-(5-bromothiophene)-2,2^′,6^′,2″-terpyridine, are communicated. In the binuclear complex, 2,5-bis(2,2^′,6^′,2″-terpyridine-4^′yl)thiophene was used as a bridge between two Ru(II) centers. The new compounds were characterized by H NMR, UV-Vis and IR spectroscopies. Bands at ∼500 nm for the Ru(II) to terpyridine charge transfer transition and absorption bands at λ<400 nm assigned to intraligand transitions, π^*←π, centered in the tpy moiety were observed in the UV-Vis spectra of the complexes. Irradiation of the complexes in CH₃CN at 337 or 500 nm induced luminescence with maxima at ∼670 nm and lifetimes τ?10² ns. Time-resolved absorption spectroscopy revealed the formation of long-lived species during the decay of the metal to ligand charge transfer excited states. The intermediates were tentatively assigned as unstable products of ligand-substitution or orthometalation excited state reactions.     

Synthesis and pH-sensitive luminescence of bis-terpyridyl iridium(III) complexes incorporating pendent pyridyl groups

A series of iridium(III) bis-terpyridine complexes have been prepared which incorporate pendent pyridyl groups at the 4′-positions of one or both of the terpyridine (tpy) ligands. These include: three mutually isomeric homoleptic complexes, in which the nitrogen atom of the pendent pyridyl is para, meta or ortho to the C-C bond to the terpyridine; their heteroleptic analogues in which the second ligand is 4′-tolyl-terpyridine (ttpy); analogous complexes of the new ligand, 4′-(2,6-dimethylpyrid-4-yl)-terpyridine; and related complexes incorporating an additional phenyl ring interposed between the terpyridine and the pendent pyridyl group. All of the complexes are luminescent in air-equilibrated aqueous solution at room temperature. The homoleptic complexes display structured emission resembling that of unsubstituted [Ir(tpy)₂]³⁺, with luminescence lifetimes of around 1 μs under these conditions. The heteroleptic analogues give broader, red-shifted emission spectra, similar to that of [Ir(ttpy)₂]³⁺, indicating that emission in these complexes arises primarily from a lower-energy excited state associated with the 4′-tolyl-terpyridine ligand. A further red-shift for the complexes incorporating the additional phenyl ring suggests that the emissive state involves the more conjugated phenylpyridyl-appended ligand in these cases. The luminescence of all of the heteroleptic complexes investigated, except the meta-substituted system, is sensitive to the protonation state of the pendent pyridyl group, and the structure of the ligand can have a significant influence on both the magnitude of the response and the pH region over which it occurs.     

Synthesis of novel antimitotic agents based on 2-amino-3-aroyl-5-(hetero)arylethynyl thiophene derivatives

Microtubules are dynamic structures that play a crucial role in cellular division and are recognized as an important target for cancer therapy. In search of new compounds with strong antiproliferative activity and simple molecular structure, a new series of 2-amino-3-(3′,4′,5′-trimethoxybenzoyl)-5-(hetero)aryl ethynyl thiophene derivatives was prepared by the Sonogashira coupling reaction of the corresponding 5-bromothiophenes with several (hetero)aryl acetylenes. When these compounds were analyzed in vitro for their inhibition of cell proliferation, the 2- and 3-thiophenyl acetylene derivatives were the most powerful compounds, both of which exerted cytostatic effects at submicromolar concentrations. In contrast, the presence of a more flexible ethyl chain between the (hetero)aryl and the 5-position of the thiophene ring resulted in significant reduction in activity relative to the 5-(hetero)aryl acetylene substituted derivatives. The effects of a selected series of compounds on cell cycle progression correlated well with their strong antiproliferative activity and inhibition of tubulin polymerization. We found that the antiproliferative effects of the most active compounds were associated with increase of the proportion of cells in the G₂/M and sub-G₁ phases of the cell cycle.     

Synthesis of aminooxy-functionalized lanthanide(III) chelates for carbonyl-group conjugation

The syntheses of three new aminooxy-tethered lanthanide(III) chelates, compounds 1-3, incorporating DOTA (= 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid), DTPA (= diethylenetriaminepentaacetic acid), or a substituted terpyridine (2,2',2',2'-[2,2': 6',2'-terpyridine-6,6'-diylbis(methylenenitrilo)]tetraacetic acid), respectively, are described. Reagents 1-3 can be used for carbonyl 'labeling', as shown by the formation of the corresponding oxime-ether bioconjugates of naltrexone (16) and 2-deoxy-beta-D-glucose (17) (Scheme 4).     

7-(aryl/heteroaryl-2-ylethynyl)-4-phenylamino-3-quinolinecarbonitriles as new Src kinase inhibitors: addition of water solubilizing groups

New 4-phenylamino-3-quinolinecarbonitriles with a 7-ethynyl group substituted by a pyridine, phenyl or thiophene ring containing basic water solubilizing groups were prepared and evaluated as Src kinase inhibitors. Of these new analogs, potent activity was observed with compounds having a (2,4-dichloro-5-methoxyphenyl)amino group at C-4, a methoxy or ethoxy group at C-6, and a pyridyl group bearing a dimethylamine or N-methylpiperazine on the ethynyl group at C-7.     

Cobalt complexes of terpyridine ligand: crystal structure and photocleavage of DNA

Two new cobalt complexes, [Co(pytpy)(2)](ClO(4))(2), 1, and [Co(pytpy)(2)](ClO(4))(3), 2 where pytpy=pyridine terpyridine, have been synthesized and characterized. Single-crystal X-ray structure of both the complexes has been resolved. The structure shows the complexes to be a monomeric cobalt(II) and cobalt(III) species with two pytpy ligands coordinated to the metal ion to give a six coordinate complex. Both cobalt(II) and cobalt(III) complexes crystallize in meridional configuration. The interaction of these complexes with calf thymus DNA has been explored by using absorption, emission spectral, electrochemical studies and viscosity measurements. From the experimental results the DNA binding constants of 1 and 2 are found to be (1.97+/-0.15)x10(4)M(-1) and (2.7+/-0.20)x10(4)M(-1) respectively. The ratio of DNA binding constants of 1 and 2 have been estimated to be 0.82 from electrochemical studies, which is in close agreement with the value of 0.73 obtained from spectral studies. The observed changes in viscosity of DNA in the presence of increasing amount of complexes 1 and 2 suggest intercalating binding of these complexes to DNA. Results of DNA cleaving experiments reveal that complex 2 efficiently cleaves DNA under photolytic conditions while complex 1 does not cleave DNA under similar conditions.     

Synthesis and characterization of novel substituted thiophene derivatives and discovery of their carbonic anhydrase and acetylcholinesterase inhibition effects

Novel substituted thiophene derivatives ( 1, 2a‐e, 3, and 4 ) were synthesized and their structures were characterized by infrared radiation, nuclear magnetic resonance, and mass analysis. These novel substituted thiophene derivatives were effective inhibitor compounds of the carbonic anhydrase I and II isozymes (hCA I and II), and acetylcholinesterase (AChE) enzyme with K _i values in the range of 447.28 to 1004.65 nM for hCA I, 309.44 to 935.93 nM for hCA II, and 0.28 to 4.01 nM for AChE, respectively. Novel substituted thiophene derivatives can be good candidate drugs for the treatment of some diseases like neurological disorders, epilepsy, glaucoma, gastric and duodenal ulcers, mountain sickness, or osteoporosis as carbonic anhydrase isozymes inhibitors, and for the treatment of Alzheimer’s and Parkinson’s diseases as acetylcholinesterase inhibitors.     

Unsymmetrical C-substituted ethylenediamine platinum coordination complexes: synthesis and activity against mouse leukemia L1210.

A series of new unsymmetrical C-substituted ethylenediamines was prepared. The substituents included branched chain alkyl, cycloalkyl, and phenyl groups. Twenty-eight new platinum compounds were prepared from these diamines and were tested for activity against leukemia L1210. The cycloalkyl substituted ethylenediamines produced especially active compounds. The phenyl-substituted analogs were generally low in activity. The activity of the complexes was compared to aqueous solubility, organic solubility, and amphipathic character. There was good indication that antitumor activity increased as aqueous solubility and hydrophilic character of the molecules increased.     

DNA‐binding affinity and nuclease activity of two cytotoxic copper terpyridine complexes

Two copper(II) terpyridine complexes, [Cu(atpy)(NO₃)(H₂O)](NO₃) ? 3H₂O ( 1 ) and [Cu(ttpy)(NO₃)₂] ( 2 ) (atpy = 4′‐p‐N9‐adeninylmethyl‐phenyl‐2,2′:6,2″‐terpyridine; ttpy = 4′‐p‐tolyl‐2,2′:6,2″‐terpyridine) exhibited high cytotoxicity, with average ten times more potency than cisplatin against the human cervix carcinoma cell line (HeLa), the human liver carcinoma cell line (HepG2), the human galactophore carcinoma cell line (MCF7), and the human prostate carcinoma cell line (PC‐3). The cytotoxicity of the complex 1 was lower than that of the complex 2 . Both complexes showed more efficient oxidative DNA cleavage activity under irradiation with UV light at 260 nm than in the presence of ascorbic acid. Especially, complex 1 exhibited evident photoinduced double‐stranded DNA cleavage activity. The preliminary mechanism experiments revealed that hydrogen peroxide was involved in the oxidative DNA damage induced by both complexes. From the absorption titration data, the DNA‐binding affinity of the complexes with surpersoiled plasmid pUC19 DNA, polydAdT, and polydGdC was calculated and complex 2 showed higher binding affinity than complex 1 with all these substrates. The DNA cleavage ability and DNA‐binding affinity of both complexes depended on the substituent group on the terpyrdine ligands. © 2009 Wiley Periodicals, Inc. J Biochem Mol Toxicol 23:295–302, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/jbt.20292     

Design, synthesis, and pharmacological evaluation of some 2-[4-morpholino]-3-aryl-5-substituted thiophenes as novel anti-inflammatory agents: generation of a novel anti-inflammatory pharmacophore

Compounds incorporating a thiophene moiety, a pi excess five membered heterocycle, have attracted a great deal of research interest owing to the therapeutic utility of the template as useful drug molecular scaffolding. Recently we reported the anti-inflammatory activity profile exhibited by two thiophene analogs, AP84 and AP82 in acute and chronic models of inflammation. The good activity profile exhibited by AP84, a 3-(substituted aryl)-2-(4-morpholino)-5-heteroaryl substituted analog of thiophene, in the formalin induced rat paw edema chronic model as compared to a weak activity in acute carrageenin induced rat paw edema, and the slightly better protection exhibited in the acute model by AP82 (27%), the 5-aroyl analog provided an impetus for a proper exploration of their structural types. In this paper we report the synthesis and pharmacological evaluation of some novel, 2-(4-morpholino)-3-(substituted aryl)-5-substituted thiophenes, as possible anti-inflammatory leads. The 3-(4-chlorophenyl)-2-(4-morpholino) thiophene analogs AP49, AP158, and AP88 provided a protection of 20%, 23%, and 20%, respectively, when screened for anti-inflammatory activity in carrageenin induced rat paw edema, an acute in vivo model, comparable to that of AP82, at a dose level of 100mg/kg body weight p.o. compared to ibuprofen as standard. The replacement of the 3-(4-chlorophenyl) moiety with the 3-phenyl moiety gave rise to AP50 (30%), AP159 (38%), AP27 (0%), and AP92 (38%), with three analogs being more active in the acute model. Alteration of the group para to the phenyl ring at third position, from chloro, to methyl mercapto gave rise to the 3-(4-methylmercapto-phenyl) analogs AP54 (20%), AP160 (0%), and AP73 (52%), with only one analog appearing to be better than AP82. These results indicate that 4-methane sulfonyl aroyl group at 5-position and other substituents of different quadrants of Craig plot on the phenyl moiety at the third position could lead to more potent candidates. However, alteration of aroyl to substituted pyridyl at 5-position with a phenyl group at the third position as in AP26 gave rise to much better protection (66%) again reinforcing the importance of the heteroaryl ring at the fifth position and implying its utility in the composition of a novel pharmacophore for designing better trisubstituted thiophenes as anti-inflammatory agents.     

Noncovalent binding of some new lipophilic gadolinium DTPA complexes to human serum albumin. A structure-affinity relationship

Four Gadolinium?DTPA complexes bearing long lipophilic alkyl chains were synthesized: two bis[amide] and two 4‐substituted derivatives. In two of them (one bis[amide] and one 4‐substituted), the alkyl chain ends with a carboxylate function. Their relaxometric properties in H₂O show the self aggregation of Gd?DTPA‐BdodecylAmide, the better stability of the 4‐substituted derivatives vs. Zn transmetallation, and the very good stability of Gd?(4‐(carboxyundecylisothiourea‐Bz)DTPA). Amongst the four compounds, only Gd?(4‐(carboxyundecylisothiourea‐Bz)DTPA) shows a strong interaction with human serum albumin (HSA) as demonstrated by proton relaxometry and ESI mass spectrometry. These data highlight the importance of the negative charge on the alkyl chain in the context of the interaction of Gd?(4‐substituted DTPA) derivatives with HSA.     

Chimeric immunoglobulin-T cell receptor proteins form functional receptors: implications for T cell receptor complex formation and activation

We constructed chimeric receptor chains in which an immunoglobulin heavy chain variable region (VH) from a phosphorylcholine-specific antibody is substituted for T cell receptor (Tcr) alpha and beta V regions. We demonstrate that the VH region joined to either the C alpha or the C beta region can form stable chimeric proteins in EL4 T cells. Both chimeric receptor chains associate with CD3 polypeptides in functional receptor complexes and respond to phosphorylcholine coupled to Sepharose beads. The VH-C alpha chimeric chain associates with the EL4 beta chain, while the VH-C beta chimeric protein appears to form either a homodimer or a heterodimer with the native EL4 beta chain. Thus, functional receptor complexes can be formed using two C beta regions, and the C alpha region may not be required for CD3 association and surface expression of Tcr complexes.     

The crystal structures of human alpha-thrombin complexed with active site-directed diamino benzo[b]thiophene derivatives: a binding mode for a structurally novel class of inhibitors

The crystal structures of four active site-directed thrombin inhibitors, 1-4, in a complex with human alpha-thrombin have been determined and refined at up to 2.0 A resolution using X-ray crystallography. These compounds belong to a structurally novel family of inhibitors based on a 2,3-disubstituted benzo[b]thiophene structure. Compared to traditional active-site directed inhibitors, the X-ray crystal structures of these complexes reveal a novel binding mode. Unexpectedly, the lipophilic benzo[b]thiophene nucleus of the inhibitor appears to bind in the S1 specificity pocket. At the same time, the basic amine of the C-3 side chain of the inhibitor interacts with the mostly hydrophobic proximal, S2, and distal, S3, binding sites. The second, basic amine side chain at C-2 was found to point away from the active site, occupying a location between the S1 and S1' sites. Together, the aromatic rings of the C-2 and C-3 side chains sandwich the indole ring of Trp60D contained in the thrombin S2 insertion loop defined by the sequence "Tyr-Pro-Pro-Trp." [The thrombin residue numbering used in this study is equivalent to that reported for chymotrypsinogen (Hartley BS, Shotton DM, 1971, The enzymes, vol. 3. New York: Academic Press. pp 323-373).] In contrast to the binding mode of more classical thrombin inhibitors (D-Phe-Pro-Arg-H, NAPAP, Argatroban), this novel class of benzo[b]thiophene derivatives does not engage in hydrogen bond formation with Gly216 of the thrombin active site. A detailed analysis of the three-dimensional structures not only provides a clearer understanding of the interaction of these agents with thrombin, but forms a foundation for rational structure-based drug design. The use of the data from this study has led to the design of derivatives that are up to 2,900-fold more potent than the screening hit 1.     

Synthesis, characterization, photophysical and photochemical properties of 7-oxy-3-methyl-4-phenylcoumarin-substituted indium phthalocyanines

The synthesis of tetra- and octa-(7-oxy-3-methyl-4-phenylcoumarin)-substituted indium(III) phthalocyanine complexes obtained from 3-nitrophthalonitrile, 4-nitrophthalonitrile and 4,5-dichlorophthalonitrile substituted with 7-oxy-3-methyl-4-phenylcoumarin are described for the first time in this study. The new compounds have been characterized by elemental analysis, IR, ¹H NMR, electronic spectroscopy and mass spectra. The photophysical and photochemical properties of the compounds are also studied in dimethylformamide (DMF). The effects of the number of the substitution and the position on the photophysical and photochemical parameters of the substituted indium(III) phthalocyanine complexes are also reported. Photophysical and photochemical properties of phthalocyanine complexes are very useful for photodynamic therapy (PDT) of cancer applications. In particular, high singlet-oxygen quantum yields are very important for Type II mechanisms. These complexes have good singlet-oxygen quantum yields and show potential as Type II photosensitizers.     

Terpyridine platinum(II) complexes inhibit cysteine proteases by binding to active-site cysteine

Platinum(II) complexes have been demonstrated to form covalent bonds with sulfur-donating ligands (in glutathione, metallothionein and other sulfur-containing biomolecules) or coordination bonds with nitrogen-donating ligands (such as histidine and guanine). To investigate how these compounds interact with cysteine proteases, we chose terpyridine platinum(II) (TP-Pt(II)) complexes as a model system. By using X-ray crystallography, we demonstrated that TP-Pt(II) formed a covalent bond with the catalytic cysteine residue in pyroglutamyl peptidase I. Moreover, by using MALDI (matrix-assisted laser desorption/ionization) and TOF-TOF (time of flight) mass spectrometry, we elucidated that the TP-Pt(II) complex formed a covalent bond with the active-site cysteine residue in two other types of cysteine protease. Taken together, the results unequivocally showed that TP-Pt(II) complexes can selectively bind to the active site of most cysteine proteases. Our findings here can be useful in the design of new anti-cancer, anti-parasite or anti-virus platinum(II) compounds.     

Oligodeoxynucleotides covalently linked to intercalating dyes as base sequence-specific ligands. Influence of dye attachment site.

New molecules with high and specific affinity for nucleic acid base sequences have been synthesized. They involve an oligodeoxynucleotide covalently attached to an intercalating dye. Visible absorption spectroscopy and fluorescence have been used to investigate the binding of poly(rA) to octadeoxythymidylates substituted by a 9-aminoacridine derivative in different positions along the oligonucleotide chain. The 9-amino group of the acridine dye was linked through a polymethylene bridge to the 3''-phosphate, the 5''-phosphate, the fourth internucleotidic phosphate or to both the 3''- and 5''-phosphates. Different interactions of the acridine dye were exhibited by these different substituted oligodeoxynucleotides when they bind to poly(rA). The interaction was shown to be specific for adenine-containing polynucleotides. The stability of these complexes was compared with that of oligodeoxynucleotides substituted by an alkyl group on the 3''-phosphate. The increase in stability due to the presence of the intercalating dye has been determined from the comparison of melting temperatures. These results are discussed with respect to the strategy of synthesis of a new class of molecules with high affinity and high specificity for nucleic acid base sequences.     

Band Gap Control in Diketopyrrolopyrrole‐Based Polymer Solar Cells Using Electron Donating Side Chains

We compare the opto‐electronic and photovoltaic properties of two diketopyrrolopyrrole (DPP) based semiconducting polymers in which the DPP unit alternates along the chain with a conjugated bis(dithienyl)phenylene (4TP) unit. The two polymers differ only in the solubilizing substituents on the thiophene rings which are either alkyl (PDPP4TP) or alkoxy (PDPP4TOP) groups. We show that alkoxy groups lower the optical band gap and increase the ionization potential compared to the alkyl groups. As a result, PDDP4TOP provides a significantly higher charge generation efficiency and concomitant higher short‐circuit current, 18.0 mA cm^?2 vs. 12.4 mA cm^?2, compared to PDPP4TP in optimized devices with [6,6]phenyl‐C₇₁‐butyric acid methyl ester ([70]PCBM) as acceptor, but a simultaneous decrease in open circuit voltage, 0.51 vs. 0.67 V. The increased current arises from a higher external quantum efficiency and a wider spectral coverage. The net result is a small increase in power conversion efficiency from 5.8% for PDPP4TP to 6.0% for the PDPP4TOP in optimized devices. The optimized processing conditions and bulk heterojunction morphology are virtually identical for both photoactive layers. The study demonstrates that the side chains enable effective method for rationally designing new photoactive semiconducting polymers.     

Design and synthesis of new types of oligonucleopeptides

Summary Design and synthesis of oligonucleopeptides (ONPs), structural analogues of oligonucleotides, where the phosphodiester backbone is substituted by a peptide chain, are described. Oligonucleopeptides, in which the number of ordinary bonds between the nucleobases is six and the number of bonds between the backbone and nucleobase is two or four were constructed using two different approaches. The first way is based on incorporation of thyminylalanine residues into the peptide chain alternatively with glycine residues. Experimental studies of the stability of oligonucleotide-oligonucleopeptide complexes as well as model estimations of their potential surfaces indicated the low DNA binding efficiency of this type of reagents. The second approach consists of synthesis of ω-ornithine peptides followed by modification of the backbone with thyminylacetaldehyde attached to an α-amino function of ornithine residues through Schiff bases. ONPs were synthesized using the solid-phase method.     

Further studies on toxic and radiosensitizing properties of ruthenium complexes of 4-nitroimidazoles

Transition metal complexes containing nitroimidazole ligands have been shown previously to act as radiosensitizers of hypoxic cells in vitro. As part of our study on metal-radiosensitizer complexes, we were encouraged by a ruthenium (Ru) sensitizer, RuCl2(DMSO)2(4(5)-nitroimidazole)2, 1, which showed better radiosensitizing properties and lower toxicity than the free ligand. In this study, we have extended our investigation to include the various other substituted 4-nitroimidazoles as ligands. The new Ru complexes, analogues of 1, were synthesized, identified and characterized and their toxicity and radiosensitizing abilities examined in vitro using Chinese hamster ovary (CHO) cells. Like 1, each of these ruthenium complexes has lower CHO hypoxic toxicity than the free ligands alone at equimolar concentration. These newer complexes gave sensitizing enhancement ratio (SER) values of 1.1 to 1.3 at 1.0 X 10(-4) mol dm-3 compared with 1.6 for 1. Unlike complex 1, the new complexes do not bind to plasmid DNA (assessed by inhibition of restriction endonuclease activity), possibly because the chloride (Cl-) ligand does not dissociate. In addition, the redox potential of the coordinated imidazole ligands is relatively unchanged compared to that of the free ligand. These factors may explain the more favourable properties of 1 compared with those of the new 4-nitroimidazole complexes of Ru.