Journal of Inorganic Biochemistry
Volume 100, Issue 3,
March 2006
, Pages 331-343
Author links open overlay panel, , , , , , ,
Abstract
Complexes of the type [Co(LL)2Cl2]Cl, where LL=N,N′-ethylenediamine (en), 2,2′-bipyridine (bpy), 1,10-phenanthroline (phen), 1,10-phenanthroline-5,6-dione (phendione) and dipyrido[3,2-a:2′,3′-c]phenazine (dppz) have been synthesized and characterized by elemental analyses, IR, UV–visible and NMR spectroscopy. Crystal structure of [Co(phendione)2Cl2]Cl·0.5HCl·3.5H2O has been solved and refined to R=0.0552. The crystal is monoclinic with space group C2/c; a=25.730(2)Å, b=12.375(1)Å, c=18.979(2)Å, β=119.925(1)° and Z=8. The DNA binding characteristics of the complexes, investigated by covalent binding assay, viscosity measurements and competitive binding fluorescence measurements show that the complexes interact with DNA covalently except the complex containing the planar dppz ligand which intercalates within the base pairs of DNA. The complexes containing en, phen and phendione cleave plasmid pBR 322 DNA upon irradiation under aerobic conditions while the complex containing the dppz ligand cleaves DNA upon irradiation under inert atmosphere. Molecular modeling studies show that the minimized structure of [Co(phendione)2Cl2]+, maintained the octahedral structure while binding to the N7 of guanines and the ligand fits into the major groove without disrupting the helical structure of the B-DNA.
Introduction
Cisplatin, cis-Pt(NH3)2Cl2 and related Pt(II) complexes are used as anticancer agents in several human cancers particularly testicular and ovarian cancers [1], [2]. The action of cisplatin is dependent on the formation of cis-[Pt(NH3)2(OH2)2]2+ by sequential thermal ligand exchange resulting in the covalent binding to GpG DNA sequences forming intrastrand crosslinks disrupting cellular transcription [3], [4]. However, severe side effects especially nephrotoxicity and acquired resistance limit its widespread use in high doses [5], [6], [7]. The development of reagents that can form intrastrand crosslinks with DNA or RNA continues to be a subject of considerable interest in the areas of molecular biology and rational drug design [8]. Barton et al. initiated the binding studies of transition metal complexes with nucleic acids [9] and reported that the cis-[Ru(phen)2Cl2] (phen=1,10-phenanthroline) binds covalently to DNA and exhibits enantiomeric selectivity different from that seen on intercalation [10]. Recently, there has been an interest in the development of cisplatin analogs, which are activated by light providing a means of localizing the action thus reducing the side effects and dosage. Morrison et al. have shown that the photolysis of cis-[Cr(phen)2Cl2]+ [11], cis-[Rh(phen)2Cl2]+ [12], cis-[Rh(phen)(dppz)Cl2]+ [13] and cis-[Rh(phen)(phi)Cl2]+ [14] (phi=9,10-phenanthrolinequinonediimine, dppz=dipyrido[3,2-a:2′,3′-c]phenazine) complexes with calf-thymus DNA using long wavelength UV light result in covalent binding of the complexes to nucleic acid. These complexes are stable to hydrolysis in dark and unreactive with DNA in the absence of light. There is an evidence that binding primarily occurs to the purines with at least one adduct involving N7 of deoxyguanosine. The reaction may be thought as a prototype for the development of “photocisplatin” reagents that are light activated and could be useful for photochemotherapy of cancer. Vaidyanathan and Nair [15] have reported that cis-[Cr(dppz)2Cl2]+ complex binds to DNA by intercalation with a binding constant of 107M−1. Co (III) Xaa-Xaa-His-metallopeptides induce DNA strand scission upon photoirradiation [16] while oxygen/H2O2 activated Co(II) complex of a macrocyclic ligand based on 1,10-phenanthroline acts as a bulge-specific probe for DNA [17] and vanadyl(IV) complexes derived from N-salicylidene α-amino acids serve as efficient DNA photocleavage agents [18].
As a part of a project aimed at studying the role of ancillary ligands on DNA binding mode we report here the syntheses, characterization, covalent DNA binding and photocleavage studies of [Co(LL)2Cl2]Cl complexes, where LL=N,N′-ethylenediamine, 2,2′-bipyridine, 1,10-phenanthroline, 1,10-phenanthroline-5,6-dione and dipyrido[3,2-a:2′,3′-c]phenazine.
Section snippets
Materials and methods
Chemicals and solvents of analytical grade were used as received. Calf thymus DNA and plasmid pBR322 DNA were obtained from SRL (India) and Bangalore Genei (Bangalore, India), respectively. The enzymes used as scavengers in the DNA cleavage studies superoxide dismutase (SOD EC1.15.1.1) and catalase (EC 1.11.1.6) were purchased from Sigma Chemical Co., USA and used as received. Deionised water was used for the preparation of the buffers. Sephadex G-25,150 was obtained from Aldrich Chemical Co.,
Syntheses
The complexes [Co(LL)2Cl2]Cl where LL=en, bpy, phen, phendione and dppz were prepared by chlorine gas oxidation resulting in green to violet crystalline solids. Single crystals of [Co(phendione)2Cl2]Cl were obtained by slow evaporation of methanol and dilute hydrochloric acid solution.
Crystal structure of [Co(phendione)2Cl2]Cl
The ORTEP diagram of the cation [Co(phendione)2Cl2]+ with the atom numbering is shown in Fig. 1. Crystal refinement and data collection is tabulated in Table 1 and selected bond lengths and angles are given in
Conclusions
From covalent binding assay, viscosity studies and fluorescence quenching it is observed that [Co(dppz)2Cl2]+ interacts with DNA by intercalation while other complexes bind covalently to the DNA double helix retaining the overall structure of the helix , which is supported by the molecular modeling studies. The complexes containing en, phen and phendione cleave plasmid pBR 322 DNA upon irradiation under aerobic conditions while the complex containing the dppz ligand cleaves DNA upon irradiation
Abbreviations
- bpy
2,2′-bipyridine
- dppz
dipyrido[3,2-a:2′,3′-c]phenazine
- en
N,N′-ethylenediamine
- phen
1,10-phenanthroline
- phendione
1,10-phenanthroline-5,6-dione
- phi
9,10-phenanthrolinequinonediimine
- CT DNA
calf thymus DNA
- DMF
N,N′-dimethyl formamide
- DMSO
dimethyl sulfoxide
- EB
ethidium bromide
- EDTA
ethylenediaminetetraacetic acid
- ESFF
extensible systematic force field
- PDB
protein databank
- SOD
superoxide dismutase
- Tris
tris(hydroxymethyl)aminomethane
See AlsoA novel μ-oxo-diruthenium(III,III)-ibuprofen-(4-aminopyridine) chloride derived from the diruthenium(II,III)-ibuprofen paddlewheel metallodrug shows anticancer properties9: Metals in MedicineRégulation des structures organométalliques de zirconium défectueuses dans un liquide ionique pour le traitement des eaux usées- UV–Vis
UV–visible
Acknowledgements
A.A.K. and A.S.K. acknowledge the financial assistance from CSIR (EMR II/00(1688)), New Delhi, India. A.C.B. acknowledge financial assistance from University of Pune. The authors thank Director C-DAC, Pune for facilities and expertise available with the Bioinformatics team at C-DAC, Pune.
References (48)
- C.X. Zhang et al.
Curr. Opin. Chem. Biol.
(2003)
- N. Farrell
Coord. Chem. Rev.
(2002)
- M.A. Billadeau et al.
J. Inorg. Biochem.
(1995)
- T. Mohammad et al.
Bioorg. Med. Chem. Lett.
(1999)
- V.G. Vaidyanathan et al.
J. Inorg. Biochem.
(2003)
- H. Chao et al.
J. Inorg. Biochem.
(2002)
- X.L. Wang et al.
J. Inorg. Biochem.
(2004)
- Q.L. Zhang et al.
J. Inorg. Biochem.
(2001)
- A.M. Jakupec et al.
Rev. Physiol. Biochem. Pharmacol.
(2003)
- E.S. Sherman et al.
J. Am. Chem. Soc.
(1988)
Chem. Rev.
(1999)
Chem. Rev.
(2003)
Chem. Rev.
(1999)
Chem. Rev.
(1998)
Chem. Rev.
(1999)
J. Am. Chem. Soc.
(1985)
J. Am. Chem. Soc.
(1992)
Inorg. Chem.
(2004)
J. Am. Chem. Soc.
(2000)
Angew. Chem. Int. Ed. Engl.
(1999)
Org. Lett.
(2004)
Bull. Chem. Soc. Jpn.
(1992)
Aust. J. Chem.
(1970)
Inorg. Synth.
(1946)
Cited by (119)
Dithiocarbazate based oxidomethoxidovanadium(V) and mixed-ligand oxidovanadium(IV) complexes: Study of solution behavior, DNA binding, and anticancer activity
2022, Journal of Inorganic Biochemistry
In this work, one oxidomethoxidovanadium(V) [VVO(L)(OMe)] (1) and two mixed-ligand oxidovanadium(IV) [VIVO(L)(phen)] (2), and [VIVO(L)(bipy)] (3) complexes have been synthesized using a tridentate bi-negative ONS donor dithiocarbazate as main ligand, H2L [where, H2L=S-benzyl-3-(2-hydroxy-3-ethoxyphenyl)methylenedithiocarbazate] along with 1,10-phenanthroline (phen) (for 2) and 2,2′-bipyridine (bipy) (for 3) as co-ligands. The ligand and complexes have been characterised by FT-IR, UV–vis, NMR, and HR-ESI-MS techniques. Distorted square pyramidal for 1, and distorted octahedral geometry for 2 and 3 was confirmed by single crystal X-ray crystallography. The behavior of 1–3 in solution medium has been investigated through various physicochemical techniques. It is observed that 1 completely and 2–3 partially decomposes and converts into a penta-coordinated species, [VIVO(L)(DMSO/H2O)] after the release of the methoxido group (1) or breaking of the diimine based co-ligands (2 and 3) in DMSO/aqueous solution. Interestingly, in DMSO/aqueous solution, 1 gets completely reduced and converted into the corresponding oxidovanadium(IV) species. Interaction of 1–3 with calf thymus DNA (CT-DNA) was investigated and the results show, complex 2 exhibited the maximum binding constants, Kb=7.12×104M−1. The anticancer potential of 1–3 was evaluated by cell viability assay against human breast carcinoma cell, MCF-7, and noncancerous mouse embryonic cell, NIH-3T3 and 2 was found to be the most cytotoxic complex (IC50=6.73±0.36μM) in the series. In addition, 2 selectively inhibit colony formation compared to the rest complexes. Also, the cell cycle studies of the complexes were performed using flow cytometry analysis.
Effect of the replacement of tripodal 4N donors by two 2N chelators on the redox and cytotoxic activity of maltolato and deferipronato containing Co(III) complexes
2021, Journal of Inorganic Biochemistry
Fourteen novel CoIII ternary complexes with the general formula [Co(4N)(2O)]X2 or [Co(2N)2(2O)]X2 where 4N=tris(2-aminoethyl)amine (tren) or tris(2-pyridylmethyl)amine (tpa); 2N=1,10-phenantroline (phen), 2,2′-bipyridine (bipy), 1,2-diaminoethane (en) or 2-(aminomethyl)pyridine (ampy) and 2O=1,2-dimethyl-3-hydroxy-4(1H)-pyridinone (dhpH), 3-hydroxy-2-methyl-4-pyrone (maltH) or 2-ethyl-3-hydroxy-4H-pyran-4-one (etmaltH) were synthesized, characterized and their redox features explored. Molecular structure of some selected [Co(2N)2(2O)](ClO4)2 (2N=phen, bipy, en; 2O=dhp, malt) or [Co(4N)(2O)](ClO4)2 (4N=tpa; 2O=etmalt) type complexes were assessed by X-ray diffraction and showed the expected octahedral geometry. Replacement of the 4N donor ligands by two 2N donor ligands resulted in the decrease of the cathodic peak potential of the complexes indicating easier reduction and allowing therefore the tailoring of the redox properties of the complexes. Screening of selected compounds against a human derived cancer cell line, HeLa, showed that, unlike the [Co(4N)(2O)]X2 derivatives, the complexes containing 2N=bipy or phen ligands have better anticancer activity than cisplatin or carboplatin.
N-substituted 2-pyridinecarbothioamides and polypyridyl mixed-ligand cobalt(III)-containing complexes for photocatalytic hydrogen generation
2020, Inorganica Chimica Acta
Citation Excerpt :
The imine CN stretching frequency mixes with the CC stretch for two bands at 1657 and 1678 cm−1. The syntheses of the complexes 3 and 4 were achieved via a two-step protocol, from complexes 1 and 2 ([Co(NN)Cl2]Cl species) which were prepared by a literature method [103]. Complexes 1 and 2 were then reacted with two equivalences of the PCA-(CF3)2 in ethanol (Scheme 2). [
Two mixed-ligand cobalt(III) complexes containing 2,2′-bipyridine (bpy) or 1,10-phenanthroline (phen), and N-(3,5-bis(trifluoromethyl)phenyl)pyridine-2-carbothioamide (PCA-(CF3)2) as ligands were synthesized, and characterized by a variety of spectroscopic techniques and elemental analyses. Crystals of the PCA-(CF3)2 molecule are of the monoclinic, C2/c crystal system and space group as determined via X-ray crystallography. The voltammetric properties of six cobalt(III) complexes, [Co(bpy)2Cl2]Cl 1, [Co(phen)2Cl2]Cl 2, [Co(bpy)2(PCA-(CF3)2)](PF6)2·H2O 3, [Co(phen)2(PCA-(CF3)2)](PF6)2·1.25H2O 4, [Co(bpy)3](PF6)3 5, and [Co(phen)3](PF6)3 6, were compared to assess the potential influence of the PCA-(CF3)2 ligand on the effectiveness of cobalt in the catalytic hydrogen evolution reaction (HER) under electrochemical and photochemical conditions. The PCA-(CF3)2 moiety caused an anodic shift in the reduction potential of CoII/I redox couple of complexes 3 and 4, in comparison to the other complexes. Complexes 3 and 4 demonstrated catalytic HER in the presence of p-cyanoanilinium tetrafluoroborate in CH3CN, with overpotentials for the HER of 730 and 630mV for complexes 3 and 4, respectively. The reduction potentials suggest that the HER was most likely facilitated by a homolytic pathway. Complexes 3 and 4 also demonstrated photocatalytic HER in the presence of [Ru(bpy)3](PF6)2 as a photosensitizer and triethanolamine as a sacrificial reductant in DMF. Complexes 3 and 4 attained rates of 2700mmol H2.mol−1 CAT min−1 and 2600mmol H2 mol−1 CAT min−1, respectively, compared to a standard complex [Co(dmgH)2(py)Cl] which had a rate of 4500mmol H2 mol−1 CAT min−1, under similar conditions. Turnover numbers (TON) of 140 were observed for [Co(dmgH)2(py)Cl] and complex 4, compared to 91 for complex 3, over a 3h period.
Synthesis, characterization, DNA binding, topoisomerase inhibition, and apoptosis induction studies of a novel cobalt(III) complex with a thiosemicarbazone ligand
2020, Journal of Inorganic Biochemistry
In this study, 9-anthraldehyde-N(4)-methylthiosemicarbazone (MeATSC) 1 and [Co(phen)2(O2CO)]Cl·6H2O 2 (where phen = 1,10-phenanthroline) were synthesized. [Co(phen)2(O2CO)]Cl·6H2O 2 was used to produce anhydrous [Co(phen)2(H2O)2](NO3)3 3. Subsequently, anhydrous [Co(phen)2(H2O)2](NO3)3 3 was reacted with MeATSC 1 to produce [Co(phen)2(MeATSC)](NO3)3·1.5H2O·C2H5OH 4. The ligand, MeATSC 1 and all complexes were characterized by elemental analysis, FT IR, UV–visible, and multinuclear NMR (1H, 13C, and 59Co) spectroscopy, along with HRMS, and conductivity measurements, where appropriate. Interactions of MeATSC 1 and complex 4 with calf thymus DNA (ctDNA) were investigated by carrying out UV–visible spectrophotometric studies. UV–visible spectrophotometric studies revealed weak interactions between ctDNA and the analytes, MeATSC 1 and complex 4 (Kb = 8.1 × 105 and 1.6 × 104 M−1, respectively). Topoisomerase inhibition assays and cleavage studies proved that complex 4 was an efficient catalytic inhibitor of human topoisomerases I and IIα. Based upon the results obtained from the 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assay on 4T1-luc metastatic mammary breast cancer cells (IC50 = 34.4 ± 5.2 μM when compared to IC50 = 13.75 ± 1.08 μM for the control, cisplatin), further investigations into the molecular events initiated by exposure to complex 4 were investigated. Studies have shown that complex 4 activated both the apoptotic and autophagic signaling pathways in addition to causing dissipation of the mitochondrial membrane potential (ΔΨm). Furthermore, activation of cysteine-aspartic proteases3 (caspase 3) in a time- and concentration-dependent manner coupled with the ΔΨm, studies implicated the intrinsic apoptotic pathway as the major regulator of cell death mechanism.
Microheterogeneous mediated electron transfer reaction (ETR) of surfactant cobalt(III) complexes by Fe<sup>2+</sup>: Effect of pyridine substituent as co ligand
2019, Arabian Journal of Chemistry
The outer sphere electron transfer reaction of surfactant cobalt(III) complexes, Cis-[Co(en)2(4CNP)(C12H25NH2)](ClO4)3 1, Cis-[Co(trien)(4CNP)(C12H25NH2)](ClO4)3 2 and Cis-[Co(trien)(4AMP)(C12H25NH2)](ClO4)3 3 (en: ethylenediamine, trien: triethylenetetramine, 4CNP: 4-cyanopyridine, 4AMP: 4-aminopyridine, C12H25NH2: dodecylamine) have been investigated by Fe2+ ion in liposome vesicles (DPPC) and ionic liquids medium at different temperatures under pseudo first order conditions using an excess of the reductant. In the presence of ionic liquid medium the second order rate constant for this electron transfer reaction was found to increase with increasing concentration of ionic liquids. Below the phase transition temperature of DPPC, the rate decreased with increasing concentration of DPPC, while above the phase transition temperature the rate increased with increasing concentration of DPPC for the same complexes has also been studied. Experimentally the reactions were found to be second order and the electron transfer postulated as outer sphere. The results have been discussed in terms of increased hydrophobic effect, self aggregation and the presence of pyridine ligand containing 4-amino and 4-cyano substituent.
Synthesis, structure and magnetic properties of a binuclear Co(II)-pyrophosphate complex, [Co<inf>2</inf>(phenanthroline-dione)<inf>4</inf>(P<inf>2</inf>O<inf>7</inf>)]
2019, Polyhedron
A series of Co(II)-1,10-phenanthroline-5,6-dione (phendione) complexes were prepared as scaffolds for the incorporation of pyrophosphate or methylenediphosphonate bridging ligands. Minor modifications in reaction conditions yielded the mononuclear complexes [Co(phendione)(H2O)4](SO4)·2H2O (1) and methylenediphosphonate complex [Co(phendione)(H2O3PCH2PO3H)(H2O)2]Cl·3H2O (2). A bridged binuclear complex, [Co2(phendione)4(P2O7)]·nH2O (3) was also prepared and structurally characterized. The magnetic properties of 3 were investigated.
Recommended articles (6)
Research article
Synthesis and redox properties of mono-, di- and tri-metallic platinum-ethynyl complexes based on the trans-Pt(C6H4N{C6H4OCH3-4}2)(CCR)(PPh3)2 motif
Polyhedron, Volume 86, 2015, pp. 31-42
The Pt-halide complex trans-PtI{C6H4NAr2}(PPh3)2 (Ar=C6H4OMe-4, 3) was prepared by oxidative addition of N(C6H4I)Ar2 (2) to Pt(PPh3)4. Reactions of trans-PtI{C6H4NAr2}(PPh3)2 (3) with 1-alkynes under CuI catalysed dehydrohalogenation conditions allows the preparation of a range of platinum ethynyl compounds containing up to four redox-active triarylamine centres. The compounds trans-Pt(C
CAr)(C6H4NAr2)(PPh3)2 (4a), trans-Pt(CCC6H4NAr2)(C6H4NAr2)(PPh3)2 (4b), {trans-Pt(C6H4NAr2)(PPh3)2}2(μ-CC-1,4-C6H4CC) (5) and N{C6H4CCPt(C6H4NAr2)(PPh3)2}3 (6) undergo a single electrochemical event for each chemically distinct type of triarylamine in the molecular backbone. The complete reversibility of the larger systems means that they can be used for charge storage materials capable of releasing up to four electrons. A combination of electrochemical, spectroelectrochemical and quantum chemical analyses reveal weak electronic coupling between the amine moieties in the redox products derived from one-electron oxidation.Research article
Maximizing dopant photoluminescence in co-doped semiconductor nanoparticles for multiplex assays by tuning inter dopant electronic interactions: Synthetic co-doping or physical mixing of singly doped moieties?
Journal of Luminescence, Volume 203, 2018, pp. 257-266
Evaluation of inter dopant electronic interactions is important to maximize photoluminescence for their use as multiplex assays. This work compares the photophysical properties of lanthanide dopants in cases where the lanthanide moieties have been either synthetically co-doped in nanoparticles or two singly doped nanoparticles were physically mixed post-synthetically. Nd3+ − Sm3+ and Nd3+ − Er3+ were considered as dopants in the TiO2 nanoparticles. Remarkable differences in lanthanide emission have been observed between the two strategies of forming the multiple and distinct lanthanide containing assemblies. The inter lanthanide electronic interactions were found to be evident in the synthetic co-doping, with the same being absent in the physically mixed assembly. As a consequence, the Nd3+ emission in near infrared (NIR) and Sm3+, Er3+ emission in visible spectral range respectively have been found to be more pronounced in the physically mixed assembly as compared to that in the synthetically co-doped nanoparticles. The situation is however reversed for the Er3+ emission in NIR spectral range. These findings collectively provide a facile way to maximize dopant emission and indicate the importance of tuning the inter lanthanide electronic interactions for better suitability as multiplex agent, in an as-desired way.
Research article
Copper(II) complexes with flexible polydentate bispicolylamidrazone ligands: Synthesis, structure and magnetic studies
Inorganica Chimica Acta, Volume 430, 2015, pp. 120-124
Three novel dinuclear copper(II) complex with spacer-armed bispicolylamidrazone ligands were synthesized and characterized by elemental analysis, UV–Vis and IR-spectroscopy and X-ray crystal analysis. Structural analysis demonstrated quite long distances (6–8Å) between copper(II) ions. Despite these long distances, antiferromagnetic interaction between paramagnetic centers was found. Temperature dependences of magnetic susceptibility and EPR studies are in agreement with an antiferromagnetic dinuclear behavior in solid state yielding exchange parameters of −2J of 1.47–5.9cm−1.
Research article
Copper(II) complexes of N-(2-{[(2E)-2-(2-Hydroxy-(5-substituted)-benzylidene)-hydrazino]carbonyl}phenyl)benzamide ligands and heterocyclic coligands
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, Volume 117, 2014, pp. 360-365
Some copper(II) complexes of the type [Cu(L1–3)(phen]⋅CH2Cl2 (1a–3a) and [Cu(L1–3) (bipy)]⋅CH2Cl2 (1b–3b) (where L1=N-(2-{[(2E)-2-(2-Hydroxy-benzylidene)-hydrazino]carbonyl}phenyl)benzamide, L2=N-(2-{[(2E)-2-(2-Hydroxy-(5-bromo)-benzylidene)-hydrazino]carbonyl}phenyl)benzamide, L3=N-(2-{[(2E)-2-(2-Hydroxy-(5-methoxy)-benzylidene)-hydrazino]carbonyl}phenyl)benzamide; phen=1,10-phenanthroline, bipy=2,2′-bipyridine) have been prepared and characterized on the basis of elemental analyses, IR, UV–Vis and EPR spectral studies. IR spectra indicate that the ligand L1–3 exists in the keto form in the solid state, while at the time of complexation, it tautomerises into enol form. The single crystal X-ray diffraction study of the representative complex [Cu(L1) (phen)]⋅CH2Cl2 (1a) reveals the distorted square pyramidal geometry around copper(II). Crystal data of (1a): space group=P21/n, a=11.5691(16)Å, b=11.0885(15)Å, c=24.890(4)Å, V=3166.2(8)Å3, Z=4. The electrochemical behavior of all the complexes indicate that the phen complexes appears at more positive potential as compared to those for bipy complexes, as a consequence of its stronger π acidic character. All the complexes exhibit blue–green emission as a result of the fluorescence from the intra-ligand (π→π∗) emission excited state.
Research article
Corrole-phenothiazine and porphyrin-phenothiazine dyads connected at β-position: Synthesis and photophysical properties
Dyes and Pigments, Volume 143, 2017, pp. 368-378
Two novel donor-acceptor dyads, in which phenothiazine (PTZ) connected at β-pyrrolic position of either freebase corrole (TPC) or freebase porphyrin (TPP) via vinylic spacer have been synthesized. Both the dyads were characterized by ESI-MS, IR, 1H NMR (1D and 2D 1H-1H COSY and J-Resolved), UV–Vis, Study state Fluorescence, Time-resolved fluorescence (Time-correlated single photon counting (TCSPC), Streak Camera) as well as electrochemical methods. In the absorption spectra of the dyads, both Soret and Q-bands were red shifted by 8–20nm indicating weak electronic communication between the two chromophores. However, the fluorescence emission from the PTZ of the dyad was efficiently quenched (96–99%) as compared to pristine PTZ where the dyad was excited at 310nm, which is attributed to singlet-singlet excited energy transfer. Fluorescence emission from porphyrin part of the TPP-PTZ dyad also quenched when excite the dyad at 420nm, which is ascribed to photoinduced electron transfer from ground state of PTZ to excited state of porphyrin. In contrast, when excite the corrole at 420nm in TPC-PTZ dyad, we found there are no significant changes in photophysical properties. In both the cases the solvent dependence of the rate of energy and electron transfer was observed.
Research article
Synthesis of cationic cobalt(II) complexes and their efficiency as catalysts for the polymerization of 1,3-butadiene
Inorganica Chimica Acta, Volume 414, 2014, pp. 8-14
A series of novel cationic cobalt(II) compounds accompanied by various counter ions ([BF4]−, [PF6]−, [SbF6]−) and N-bearing ligands (1,10-phenanthroline, bipyridine, benzimidazole, and imidazole) were synthesized. Neutral compounds, CoCl2-nLigands, were prepared as reference compounds. All the compounds were characterized using IR spectral analysis and elemental analysis and some of the compounds were further characterized by single-crystal X-ray diffraction analysis. The synthesized compounds were evaluated as precursors for butadiene polymerization in conjunction with ethylaluminum sesquichloride as a cocatalyst, and the polymerization mechanism was proposed to involve anionic coordination polymerization. The active centers of the catalysts were cationic in nature, and the catalytic activities were affected by the electronegativity of the counter ion.
CAr)(C6H4NAr2)(PPh3)2 (4a), trans-Pt(CCopyright © 2005 Elsevier Inc. All rights reserved.