Synthetic Metals (v.156, #11-13)
Editorial Board (iii).
Highly efficient red electroluminescence induced by efficient electron injection and exciton confinement by Ping Zhao; Xuhui Zhu; Jiangshan Chen; Dongge Ma; Wei Huang (763-768).
Highly efficient DCJTB-doped device was realized by enhanced electron injection and exciton confinement. A fluorine end-capped linear phenylene/oxadiazole oligomer 2,5-bis(4-fluorobiphenyl-4′-yl)-1,3,4-oxadiazole (1) and a trifluoromethyl end-capped oligomer 2,5-bis(4-trifluoromethylbiphenyl-4′-yl)-1,3,4-oxadiazole (2) were designed and incorporated as an electron transporting/hole blocking material in the device structure ITO/NPB (60 nm)/DCJTB:Alq3 (0.5%, 10 nm)/1 or 2 (20 nm)/Alq3 (30 nm)/LiF (1 nm)/Al (100 nm). The devices showed highly efficient red luminescence. In particular, the device based on 1 achieved pure red luminescence at 620 nm originating from DCJTB, with a narrow FWHI of 65 nm, maximal brightness of 13,300 cd/m2 at voltage of 20.8 V and current density of ca. 355 mA/cm2. High current and power efficiencies (>3.6 cd/A, 1.0 lm/W) were retained within a wide range of current densities. Our results show efficient and stable DCJTB-doped red electroluminescence could be anticipated for practical applications by taking advantage of the present approaches. The control experiments using BCP were also studied.
Keywords: DCJTB; Oxadiazole; Fluorine; Electron transporting/hole blocking; Electroluminescence;
Dedoping of organic semiconductors by D.M. Russell; T. Kugler; C.J. Newsome; S.P. Li; M. Ishida; T. Shimoda (769-772).
An effective dedoping method for organic semiconductors using tetrakisdimethylaminoethylene (TDAE) was demonstrated using poly(3-hexylthiophene) thin film transistors in top gate configuration. Devices were treated after production and showed improved on/off ratios of up to 105 with little change in the field effect mobility.
Keywords: Dedoping; Organic semiconductors; TDAE; Transistors;
Magnetic properties of polyaniline doped with FeCl3 by J.B. Gosk; I. Kulszewicz-Bajer; A. Twardowski (773-778).
Magnetic properties of polyaniline (PANI) doped with FeCl3 were investigated as a function of temperature and magnetic field. The temperature dependence of the magnetic susceptibility (χ) of PANI doped with FeCl3 exhibits dominant paramagnetic component (well described by Curie–Weiss law with a negative Curie–Weiss temperature Θ) accompanied by a small temperature-independent paramagnetic contribution. Magnetization measured as the function of magnetic field shows smaller saturation effect than expected for non-interacting iron ions. These two observations suggest weak antiferromagnetic (AF) interactions between Fe ions.
Keywords: Polyaniline; Magnetization; Lewis acid doping;
Desktop inkjet printer as a tool to print conducting polymers by Yuka Yoshioka; Ghassan E. Jabbour (779-783).
In order to exploit mechanical flexibility of organic-based electronic devices, conducting polymer anodes, such as polyaniline or poly(3,4-ethylenedioxy)-thiophene-poly(styrene sulfonate) (PEDOT-PSS), have been extensively studied. Along with the use of solution based processing techniques, conducting polymers can simplify the device fabrication procedure and yield themselves easily to printing techniques. In this paper, we present the results of utilizing desktop inkjet printer as a tool for direct printing and patterning of conducting polymer. Design of printable patterns and adjustment of printing parameters can be performed using any software such as Power Point. PEDOT-PSS suspension can be loaded into an inkjet cartridge and deposited on a given substrate in any designed pattern. The gray-scale color scheme can be employed to control the layer thickness and sheet resistivity of the inkjet printed layers. These layers are then used as anodes in organic light-emitting devices (OLEDs).
Keywords: Conducting polymers; Inkjet printing; Organic light-emitting diodes; Morphology; PEDOT-PSS;
Polymerization of thiophene containing cyclobutadiene Co cyclopentadiene complexes by Paul D. Byrne; Dongwhan Lee; Peter Müller; Timothy M. Swager (784-791).
To understand the charge transport ability of the metal coordinated cyclobutadiene, a series of cyclobutadiene cobalt cyclopentadiene (CbCoCp) complexes containing electrochemically polymerizable thiophene units were synthesized. The complexes were electrochemically polymerized and the resulting polymers were characterized by cyclic voltammetry, in situ conductivity and UV–vis spectroelectrochemistry. Several different derivatives of the CbCoCp complexes and a model study suggested that if the oxidation of the organic fragment was above CoI/II redox couple of the CbCoCp complex, detrimental side reactions occured. Side reactions did not occurred if the oxidation of the organic fragment was below the metal oxidation.
Keywords: Organometallic polythiophene derivatives; Conducting organometallic polymers; Cyclobutadiene cobalt complexes;
SEM/STM studies on the surface structure of a novel carbon fiber from lyocell by Qi-Lin Wu; Shu-Ying Gu; Jing-Hua Gong; Ding Pan (792-795).
The surface structure and strengths of two types of cellulose-based carbon fibers, rayon-based carbon fiber (RCF) and lyocell-based carbon fiber (LCF), were investigated through scanning electronic microscopy (SEM) and scanning tunneling microscopy (STM). SEM delineated much smoother surface for LCF, while rougher surface with obvious cracks and grooves for RCF. It is believed that the difference of surface structure between these two carbon fibers results in a decrease in tensile strength for RCF. It can be found from the image of STM (500 nm × 500 nm) that the surfaces of LCF are characterized by bulk structure. Furthermore, it is proven that the bulk structure is composed of the smaller slug-like microstructures, each of which has a width of about 25 nm and length of 150 nm aligned with an angle at 45° to fiber axis when the observation scales down to 50 nm × 50 nm. The distance between two adjacent carbon atoms of LCF estimated by section analysis of STM reveals that no hexagonal carbon ring is formed on the surface of LCF examined.
Keywords: Lyocell fiber; Carbon fiber; Surface structure; SEM; STM;
Polyaniline fibres containing single walled carbon nanotubes: Enhanced performance artificial muscles by Vahid Mottaghitalab; Binbin Xi; Geoffrey M. Spinks; Gordon G. Wallace (796-803).
Organic conducting fibres based on either inherently conducting polymers (polyaniline) or carbon nanotubes (CNTs) have previously been produced. In this work the integration of CNTs into polyaniline fibres has been achieved using wet spinning techniques. It is shown that addition of small amounts of CNTs significantly improves the mechanical, electronic and electrochemical properties of the polyaniline fibre. These improved properties result in increased electromechanical actuation when used as artificial muscle fibres.
Keywords: Polyaniline; Single wall carbon nanotubes; Composite fibres; Wet spinning; Artificial muscles;
Synthesis and characterization of novel low band gap polymers: Poly(heteroarylene methines) by Qinghui Zhang; Jichang Feng; Kuan Liu; Dexi Zhu; Mujie Yang; Hui Ye; Xu Liu (804-808).
A series of novel poly(heteroarylene methines) containing alternating aromatic and quinoid phenylene-thiophene moieties in the main chain were synthesized. They were readily soluble in common organic solvents, and revealed tunable band gaps. Several low band gap polymers were obtained when octoxy or decoxy groups were applied as pendent groups of phenylene unit. And relevant octoxy-substituted poly(heteroarylene methins), PDTDOBQ-Me, PDTDOBQ-ORBr and PDTDOBQ-NO2, showed electrochemical band gaps of 1.60, 1.68 and 1.76 eV, respectively.
Keywords: Low band gap; Conjugated polymers; Poly(heteroarylene methines);
N-Aryl carbazole derivatives for non-doped red OLEDs by Hui-ying Fu; Huan-rong Wu; Xiao-yuan Hou; Fei Xiao; Bing-xian Shao (809-814).
Two N-aryl carbazole derivatives: 3-2-(3,3-dicyanomethylene-5,5-dimethyl-1-cyclohexylidene)vinyl-N-naphthyl-carbazole (NCz-2CN) and 3,6-bis(2-(3,3-dicyanomethylene-5,5-dimethyl-1-cyclohexylidene)vinyl-N-phenyl-carbazole (PCz-4CN), with the molecular structure of donor-π-acceptor, have been synthesized and characterized. They are red emitters in the solid films with a peak wavelength at 630 nm of NCz-2CN and 666 nm of PCz-4CN. Non-doped orange-red electroluminescent devices with the structure of ITO/NPB/NCz-2CN/BCP/Alq3/LiF/Al were fabricated. The device showed orange-red emission at λ max = 628 nm and a maximum luminance of 4110 cd/m2 obtained at 15 V. The maximum luminous efficiency was 0.49 lm/W and the current efficiency was 2.09 cd/A.
Keywords: N-Aryl carbazole; Organic light-emitting diodes; Red emission; Non-doped device;
Effect of macromolecular parameters and processing conditions on supramolecular organisation, morphology and electrical transport properties in thin layers of regioregular poly(3-hexylthiophene) by Jean-Marie Verilhac; Gilles LeBlevennec; David Djurado; François Rieutord; Mustapha Chouiki; Jean-Pierre Travers; Adam Pron (815-823).
The effects of molecular weight and the processing conditions on the polymer supramolecular organisation, its morphology and charge carriers mobility have been investigated for regioregular poly(3-hexylthiophene) (RR-P3HT) thin layers used for the fabrication of field-effect transistors (FETs). The application of three distinctly different processing techniques (dip coating, spin coating and drop casting) together with polymers exhibiting different molecular weights, including previously unexplored molecular weight value (120 kDa by SEC equal to 27 kDa after the MALDI-TOF correction) enabled the separation of the influence of purely macromolecular factors from the morphological ones. It has been demonstrated that the chain length of the deposited polymer is the determining factor in the fabrication of layers with high carriers mobility which changes from 10−5 cm2/(V s) for the shortest chains (Mn corrected = 1 kDa) to 0.04 cm2/(V s) for the longest ones (Mn corrected = 27 kDa). The changes of the film morphology cannot explain the dependence of the mobility on Mn. The observed relationship can be rationalized by considering the principal factors, intervening on three different levels: (i) on the molecular level the increase of the conjugation length with Mn is observed which leads to a higher mobility of the carriers along a single chain; (ii) on the supramolecular level the probability of the interchain charge carriers hopping is higher for longer chains since the number of low activation energy pathways for the crossing between chains grows with the increase of the chain length; (iii) on the mesoscopic level the connectivity between aggregations of higher mobility, for example, nanorods observed by AFM, is better assured for longer polymer chains. The product of these contributions results in an enhanced carriers mobility for layers fabricated from high molecular weight polymer fractions. The morphology of the RR-P3HT layers is strongly dependent on the processing method used. For high rate deposition techniques (spin coating) nanorod-type morphologies are obtained for low molecular weight polymers whereas fractions of high molecular weight give films with a granular morphology. For low deposition rate techniques (dip coating) the rod-like morphology persists even for films fabricated from the highest molecular weight fraction. Moreover, for layers obtained from intermediate polymer fractions (from 1.9 to 10.8 kDa) the individual rod width is, within the experimental error, equal to the length of the polymer chain if the all trans conformation is assumed. The above observation implies that polymer chains are oriented perpendicularly to the rod long axis. GIXD investigations fully corroborate this hypothesis. The rod diameter in layers deposited using the highest molecular weight fraction (27 kDa) is significantly lower than the length of the chain in the all trans conformation, suggesting chain folds via all trans–all cis–all trans sequence of conformation changes which would limit the rod diameter.
Keywords: Poly(3-hexylthiophene); Field-effect transistor; Mobility; Molecular weight; Viscosity; Morphology; Nanorods;
Organic light-emitting diode based on a carbazole compound by Yingliang Liu; Cong-an Di; Yuanrong Xin; Gui Yu; Yunqi Liu; Qingguo He; Fenglian Bai; Shengang Xu; Shaokui Cao (824-827).
A carbazole compound was synthesized by Knovenagel condensation and characterized by the measurements of 1H NMR, IR and melting point. A multilayer organic light-emitting diode (OLED) using this compound as an active layer was fabricated by vacuum-deposition. This OLED showed a turn-on voltage of approximately 4.5 V and a maximum luminance of 910 cd/m2. Additionally, the maximum luminous efficiency was found as 0.95 cd/A, at this point the device luminance was measured as 146 cd/m2 at an operating voltage of 7 V. The coordinate value of CIE 1931 was calculated as (x, y) = (0.3843, 0.5345) from the electroluminescence (EL) spectrum, which suggested that the device can emit a yellow-green light.
Keywords: Carbazole; Electroluminescence; OLED;
Electrical bistability and memory applications of poly(p-phenylenevinylene) films by Swarup K. Majee; Himadri S. Majumdar; Alberto Bolognesi; Amlan J. Pal (828-832).
Devices based on oriented and unoriented poly(p-phenylenevinylene) films showed presence of electrical bistability. Depending on the voltage sweep direction, current through the device at any voltage had two values. Switching between a low- and a high-conducting state occurred when a suitable voltage pulse was applied. Impedance spectroscopy identified a change in bulk resistance of the device during the transition between the two states. Role of orientation of the polymer film on switching and electrical bistability has been studied. The bistability in these devices had an associated non-volatile memory. We have demonstrated read-only and random access memory applications in such devices using current–voltage and impedance characteristics.
Keywords: Conductance switching; Conjugated polymers; Data-storage devices; Impedance spectroscopy; Memory applications;
Electrical and magnetic properties of the composite pellets containing DBSA-doped polyaniline and Fe nanoparticles by Wenyan Xue; Hong Qiu; Kun Fang; Jing Li; Jingwei Zhao; Mei Li (833-837).
DBSA-doped polyaniline powder (DBSA-PANI) was mixed with Fe nanoparticles to obtain the DBSA-PANI-Fe composite. Powder of the composite was compacted to the pellets to study the electrical property and magnetization characteristic by measuring the conductivity in 100–300 K and the magnetization curve at room temperature. The conductivity of the composite pellet is linearly decreased from 0.25 ± 0.02 to 0.07 ± 0.01 S/cm with increasing the Fe nanoparticle content from 0 to 70 wt.%. For the pellets containing the Fe nanoparticles less than 70 wt.%, the variation of conductivity with temperature reveals that the charge transport mechanism can be considered to be one-dimensional variable-range-hopping (1D-VRH). For the pellet with 70 wt.%-Fe nanoparticles, however, the charge transport mechanism cannot be well understood in terms of the VRH model. All the DBSA-PANI-Fe composite pellets show a magnetic hysteresis loop and a hard magnetization characteristic. The saturation magnetization monotonously increases from 32 to 78 emu/g with increasing the Fe nanoparticle content from 30 to 70 wt.%. The saturation field and the coercivity are estimated to be about 5500 and 385 Oe, respectively, independent of the Fe nanoparticle content.
Keywords: DBSA-doped polyaniline; Fe nanoparticles; Composite; Conductivity; Magnetization;
Spin-coated conductive polymer film resistivity measurement using the TLM method by L. Giraudet; S. Fauveaux; O. Simonetti; C. Petit; K. Blary; T. Maurel; A. Belkhir (838-842).
Organic conductors such as PEDOT:PSS are commonly used for the fabrication of OLEDs or OTFT transistors. Conductivity measurement is mandatory to improve both material composition and process parameters, and to allow device and circuit modeling. Film deposition using spin-coating on circular TLM electrode structures is a straightforward method for extracting both the film resistance and the contact resistivity, providing an accurate model is used. A practical measurement procedure is described in detail and applied to the measurement of PEDOT:PSS solutions.
Keywords: Conductive polymer; Resistivity; Contact resistance; Transmission line method; Organic thin film transistor;
Molecular scale organized poly(MDMO-p-phenylene vinylene)–heteropolyacid composites by A.I. Kulak; A.I. Kokorin; T.I. Kulak; S.K. Poznyak; D. Meissner; V.I. Pergushev; N.S. Sariciftci (843-847).
In this study, the interaction of phosphomolybdic acid (H3PMo12O40) with poly[2-metoxy-5-(3′,7′-dimethyloctyloxy)-p-phenylene vinylene] (MDMO-PPV) has been investigated by the methods of optical absorbance and luminescence spectroscopy, electrochemical, EPR and chemical analysis. It is shown that the interaction between MDMO-PPV and H3PMo12O40 leads to the formation of charge-transfer complex, which involves one heteropolyanion per four monomer units of the polymer chain. We have demonstrated that this interaction causes reversible changes in the electronic structure of the polymer as well as the appearance of an additional line in a long-wavelength region of optical absorbance spectra, a sharp decrease of the efficiency of luminescence and the emergence of pronounced EPR signal.
Keywords: Poly(phenylene vinylene) and derivatives; Organic/inorganic interfaces; Electrochemical methods; Heteropolyacids; EPR;
Electron spin resonance measurements of iodine-doped pentacene films by W.J. Yun; J.M. Cho; J.-K. Lee (848-851).
Pentacene films, grown on polyethylene terephthalate (PET) substrates, were doped with iodine. Electron spin resonance (ESR) measurements were made for the films in the temperature range of 100–300 K. Two regimes of doping stages were discernible: a light (intercalation) doping regime and a heavy (saturation) doping regime. The light doping regime was concluded to be dominated by localized holes that were trapped at low temperatures, which indicated trap states near the valence band edge. The heavy doping regime was dominated by different localized spins following Curie behavior. The temperature-dependence of the ESR linewidths and g-values also reflected the two doping regimes.
Keywords: Organic semiconductor; Pentacene; Small molecule system; Iodine doping; ESR;
The effect of C60 doped interlayer for lifetime improvement of phosphorescent light emitting diodes by Jun Yeob Lee (852-855).
The effect of C60 doped interlayer between poly(3,4-ethylenedioxythiophene:poly(styrenesulfonate) (PEDOT) and light emitting layer on the lifetime of phosphorescent organic light emitting diodes was investigated by changing the C60 content from 0% to 3%. Doping of C60 in 1,3,5-tris(N,N-bis-(4,5-methoxyphenyl)-aminophenyl)benzol (TDAPB) resulted in the increase of lifetime by more than 100% compared with lifetime of non-doped devices.
Keywords: C60; Doping; Lifetime;
N,N-Bis(2,2-diphenylvinyl)anilines as new effective glass-forming hole transport materials for electrophotographic photoreceptors by A. Matoliukstyte; J.V. Grazulevicius; J. Jankauskas; J. Sidaravicius (856-860).
A series of N,N-bis(2,2-diphenylvinyl)anilines was synthesized by a stepwise route and characterized by nuclear magnetic resonance, infrared and mass spectrometries. The thermal, optical and photoelectrical properties of the newly synthesized compounds are reported. The synthesized compounds form glasses with the glass transition temperatures ranging 71–76 °C as characterized by differential scanning calorimetry. The electron photoemission spectra of the synthesized compounds have been recorded and the ionization potentials of 5.45–5.55 eV have been determined. The best charge transport properties were shown by N,N-bis(2,2-diphenylvinyl)-4-methoxyaniline. Room temperature hole-drift mobilities in its 50% solid solutions in bisphenol Z polycarbonate (PC-Z) established by the xerographic time-of-flight technique were found to exceed 10−4 cm2 V−1 s−1 at electric field of 106 V cm−1.
Keywords: Aromatic enamine; Glass; Ionization potential; Charge transport;
Characteristics of poly(vinyl acetate) as a gate insulating material in organic thin film transistors by J.H. Sung; S.J. Park; J.H. Park; H.J. Choi; J.S. Choi (861-864).
We report the physical characteristics of poly(vinyl acetate) (PVAc) as a polymeric gate insulator in the organic thin film transistors (OTFTs), in which the OTFTs require not only a simple packing process with a relatively low cost compared to conventional inorganic electronics but also their compatibility with flexible substrates. The PVAc gives dielectric constant values in the range of 3.2–8.3, which can be adopted as a good gate insulator for OTFTs. The fabricating condition of OTFTs using the PVAc was improved by both adjusting its viscosity with that of a medium, and controlling the surface morphology and spin coating conditions. All these meet the requirement for a new organic gate-insulator, which can improve the performance of the present OTFTs.
Keywords: Organic thin film transistor; Poly(vinyl acetate); Dielectric constant; OTFT;
Synthesis and optical properties of aluminum and zinc quinolates through styryl subsituent in 2-position by Vasilis P. Barberis; John A. Mikroyannidis (865-871).
4-Methyl(methoxy or chloro)benzaldehyde reacted with 2-methyl-8-quinolinol to afford the corresponding substituted 2-styryl-8-quinolinol. The latter was used as chelating ligand to prepare aluminum and zinc complexes. The spectroscopic, thermal, thermomechanical and optical properties of these complexes were investigated. The thermal stability of the complexes was much higher than the reference complexes AlQ3 and ZnQ2. The char yield at 800 °C in N2 for typical complexes of Al and Zn was 49–64% whereas that for the reference complexes was 13–31%. The processability of the complexes was improved since they were soluble in common organic solvents such as THF, chloroform and acetonitrile. Solutions of complexes in THF emitted blue-green light with photoluminescence (PL) maximum at 513–576 nm that is considerably red-shifted relative to AlQ3 (514 nm) and ZnQ2 (535 nm). In addition, the PL maximum in THF of the synthesized Zn complexes was red-shifted as compared to the corresponding Al complexes. The nature of the styryl substituent (methyl, methoxy or chloro) of the chelating ligand influenced also the location of the PL maximum.
Keywords: AlQ3; ZnQ2; Aluminum complex; Zinc complex; Optical properties; Styryl quinolate;
Fabrication of modified-poly(divinylbenzene)/Au core–shell structure by Kim Xuyen Phan; Misuk Cho; Jae-Do Nam; Youngkwan Lee (872-877).
A novel PDVB/Au core–shell structure was prepared by the chemical reduction of a gold–phenanthroline complex on the surface of a poly(divinylbenzene) (PDVB) cores (2–4 μm). The PDVB cores were synthesized by precipitation polymerization, and the surface was modified by introducing thiol and sulfonic acid groups. The modified surface structure was examined by FT-IR, XPS and EDS and the degree of sulfonation was measured according to its ion exchange capacity (IEC, 5.72 meq/g). The modified PDVB cores were immersed in a solution of a gold–phenanthroline complex and subsequently reduced to form gold nanoseeds. These were further grown in a solution of HAuCl4 and NH2OH to form gold nanoshells. The effects of the functional groups on the PDVB cores on fabrication of the core–shell structure were carefully examined. SEM and XPS were used to characterize the gold nanoshells. The presence of the functional groups could be of great assistance for the gold shell formation.
Keywords: Polydivinylbenzene; Gold; Core–shell; Gold–phenanthroline complex;
Electrochemical synthesis and characterization of a copolymer made from the 2-biphenyl-3-octylthiophene monomer by Rose-Marie Latonen; Jan-Erik Lönnqvist; Lars Jalander; Kaj Fröberg; Carita Kvarnström; Ari Ivaska (878-884).
An electrically conducting copolymer film synthesized by electrochemical polymerization from a comonomer molecule of 2-biphenyl-3-octylthiophene (BOT) was studied. A poly(2-biphenyl-3-octylthiophene) (PBOT) film adherent on a Pt working electrode was polymerized by potential cycling of 40 mM BOT in 0.1 M lithium hexafluoro arsenate (LiAsF6)-acetonitrile electrolyte solution. Many soluble intermediates were formed in the polymerization process. The effect of the concentration of the starting material, type of the electrolyte salt, the solvent and the scan rate used in polymerization and temperature was studied on the polymerization process of BOT. The formed PBOT film was characterized by cyclic voltammetry (CV), X-ray diffraction (XRD) analysis and electron ionization mass spectrometric (EIMS) analysis. The properties of the formed copolymer was compared with a copolymer synthesized using biphenyl and 3-octylthiophene as starting materials, poly(thienyl biphenyl) (PTB). The CV and EIMS measurements gave evidence of formation of a conductive material with a shorter effective conjugation length than in the PTB copolymer. XRD measurements showed that a semi-crystalline and rather amorphous structure was obtained in both electrochemically synthesized copolymers. But the structure of PBOT, however, was found to be according to the shape of the cyclic voltammogram and from EIMS and XRD data less cross-linked and more uniform than the structure of PTB.
Keywords: Conducting polymer; Copolymer; Cyclic voltammetry; XRD analysis; MS analysis;
Ru(II) complexes containing dihydro-1,1,3,3-tetramethyl-7,8-diazacyclopentaphenanthren-2-ol ligand: Synthesis and their electrochemiluminescent characteristics by Do Nam Lee; Hak Mook Kim; Eun Hwa Kim; Bong Kwan Soh; Chong-Hyeak Kim; Byung Min Lee; Sook Hyun Yoon; Won-Yong Lee; Byeong Hyo Kim (885-892).
A series of new ruthenium(II) complexes containing dihydro-1,1,3,3-tetramethyl-7,8-diazacyclopentaphenanthren-2-ol (DTDP-OH) ligand, such as [Ru(DTDP-OH) n (L)3−n ]2+ (L = 2,2′-bipyridyl (bpy), o-phenanthroline (o-phen), 2,2′-bipyridine-4,4′-dicarboaldehyde (bpy-(CHO)2), 1,3-dihydro-1,1,3,3-tetramethyl-7,8-diazacyclopentaphenanthren-2-one(DTDP), n = 1, 2, 3) were synthesized and their electrochemical and photophysical properties were studied. The synthesized Ru(II) complexes containing the DTDP-OH ligand showed strong MLCT absorptions at 420–487 nm. All the synthesized Ru(II) complexes containing the DTDP-OH ligand exhibited more intensive ECL emissions than the well-known [Ru(o-phen)3]2+ does. In particular, the ECL intensities of [Ru(DTDP-OH)2(o-phen)]2+ and [Ru(DTDP-OH)2(bpy-(CHO)2)]2+ were observed to be more than 2-fold greater than that of [Ru(o-phen)3]2+.
Keywords: Electrochemiluminescent; Ruthenium(II) complexes; Dihydro-1,1,3,3-tetramethyl-7,8-diazacyclopentaphenanthren-2-ol ligand;