Functionalization of ‘kite’ shaped styryl end-capped benzodithiophene with ketone groups: synthesis, characterization and properties

We report the synthesis of a new bridged end-capped distyryldithiophene with ketone groups on the bridge: E,E-2,7′-bis((2-phenyl)-ethenyl)-benzo[2,1-b:3,4-b′]dithiophene-4,5-dione 1. Optical and electrochemical properties of 1 in solution were investigated by UV-vis absorption and cyclic voltammetry and compared to the unsubstituted parent molecule (KDS2T). Morphology of 1-based thin films was investigated by scanning electron microscopy (SEM) and the crystalline structure characterization by X-ray diffraction (XRD). Thin films were implemented as active layers into organic thin-film transistors (OTFT) in top contact configuration to evaluate the charge transport properties.     

Nitrogen donor ligands bearing N–H groups: Effect on catalytic and cytotoxic activity of molybdenum η3-allyldicarbonyl complexes

Reactions of [Mo(η³-C₃H₅)Br(CO)₂(NCMe)₂] with the bidentate nitrogen ligands 2-(2′-pyridyl)imidazole (L1), 2-(2′-pyridyl)benzimidazole (L2), N,N′-bis(2′-pyridinecarboxamido)-1,2-ethane (L3), and 2,2′-bisimidazole (L4) led to the new complexes [Mo(η³-C₃H₅)Br(CO)₂(L)] (L = L1, 1; L2, 2; L4, 4) and [{Mo(η³-C₃H₅)Br(CO)₂}₂(μ-L3)] (3).The reaction of complexes 2 and 3 with Tl[CF₃SO₃] afforded [Mo(η³-C₃H₅)(CF₃SO₃)(CO)₂(L2)] (2T) and [{Mo(η³-C₃H₅)(CF₃SO₃)(CO)₂}₂(μ-L3)] (3T).Complexes 3 and 2T were structurally characterized by single crystal X-ray diffraction, showing the facial allyl/carbonyls arrangement and the formation of the axial isomer. In 2T, two molecules are assembled in a hydrogen bond dimer.The four complexes 1–4 were tested as precursors in the catalytic epoxidation of cyclooctene and styrene, in the presence of t-butylhydroperoxide (TBHP), with moderate conversions and turnover frequencies for complexes 1–3 and very low ones for 4. The increasing number of N–H groups in the complexes seems to be responsible for the loss of catalytic activity, compared with other related systems. The cytotoxic activities of all the complexes were evaluated against HeLa cells. The results showed that compounds 1, 2, 4, and 2T exhibited significant activity, complexes 2 and 2T being particularly promising.     

Synthesis and repellent properties of vinylidene fluoride-containing polyacrylates

Fluorinated polyacrylats with side group containing vinylidene fluoride (VDF) units (CF₃(CF₂)_n (CH₂CF₂)_m, n = 3, 5; m = 1, 2) were successfully synthesized. The water and oil repellency properties of these polymers are similar to those of fluorinated polyacrylate with side group containing long perfluorooctyl group (CF₃(CF₂)₇). The thermal telomerization of CF₃(CF₂)₅I and CF₃(CF₂)₃I with vinylidene fluoride (VDF) provided CF₃(CF₂)₅CH₂CF₂I (1b) and CF₃(CF₂)₃CH₂CF₂CH₂CF₂I (1c), respectively. The addition of 1b with ethylene followed by hydrolysis gave CF₃(CF₂)₅CH₂CF₂CH₂CH₂OH (2b). Treatment of 1c with ethyl vinyl ether in the presence of Na₂S₂O₄ followed by reduction produced CF₃(CF₂)₃CH₂CF₂CH₂CF₂CH₂CH₂OH (2c). Fluoroacrylates 3b-d were prepared by acrylation of the corresponding fluoroalcohols 2b-d. The semi-continuous process emulsion co-polymerization of 3a-d with octadecyl acrylate and 2-hydroxylethyl acrylate initiated by (NH₄)₂S₂O₈ in the presence of a mixture emulsifiers of polyoxyethylene(10)nonyl phenyl ether (TX-10) and sodium lauryl sulfate provided stable latexes 4a-d, respectively. The water and oil repellency properties of 4b (R_f: CF₃(CF₂)₅CH₂CF₂) and 4c (R_f: CF₃(CF₂)₃CH₂CF₂CH₂CF₂) containing vinylidene fluoride (VDF) units were similar to those of 4a (R_f: CF₃(CF₂)₇) containing long perfluoroalkyl group and much better than those of polymer 4d (R_f: CF₃(CF₂)₃) with short perfluoroalkyl chain. Thus, polyacrylates containing vinylidene fluoride units showed promising aspects as the alternatives to the currently used water and oil repellent agents with long perfluoroalkyl chains.     

Structural control in palladium(II)-catalyzed enantioselective allylic alkylation by new chiral phosphine-phosphite and pyridine-phosphite ligands

The ligands 6-[(diphenylphosphanyl)methoxy]-4,8-di-tert-butyl-2,10-dimethoxy-5,7-dioxa-6-phosphadibenzo[a,c]cycloheptene, 1, (S)-4-[(diphenylphosphanyl)methoxy]-3,5-dioxa-4-phosphacyclohepta[2,1-a;3,4a′]dinaphthalene, (S)-2, and (S)-4-[(diphenylphosphanyl)methoxy]-2,6-bis-trimethylsilanyl-3,5-dioxa-4-phosphacyclohepta[2,1-a;3,4-a′]dinaphthalene, (S)-3, (S)-2-(3,5-dioxa-4-phosphacyclohepta[2,1-a;3,4-a′]dinaphthalen-4-yloxymethyl)pyridine, (S)-4, and (S)-2-(3,5-dioxa-4-phosphacyclohepta[2,1-a;3,4-a′]dinaphthalen-4-yloxy)pyridine, (S)-5, have been easily prepared.The cationic complexes [Pd(η³-C₃H₅)(L-L′)]CF₃SO₃ (L–L′=1–(S)-5) and [Pd(η³-PhCHCHCHPh)(L–L′)]CF₃SO₃ (L–L′=(S)-2–(S)-4) were synthesized by conventional methods starting from the complexes [Pd(η³-C₃H₅)Cl]₂ and [Pd(η³-PhCHCHCHPh)Cl]₂, respectively. The behavior in solution of all the π-allyl- and π-phenylallyl-(L–L′)palladium derivatives 6–14 was studied by ¹H, ³¹P{¹H}, ¹³C{¹H} NMR and 2D-NOESY spectroscopy. As concerns the ligands (S)-4 and (S)-5, a satisfactory analysis of the structures in solution was possible only for palladium–allyl complexes [Pd(η³-C₃H₅)((S)-4)]CF₃SO₃, 11, and [Pd(η³-C₃H₅)((S)-5)]CF₃SO₃, 12, since the corresponding species [Pd(η³-PhCHCHCHPh)((S)-4)]CF₃SO₃, 13, and [Pd(η³-PhCHCHCHPh)((S)-5)]CF₃SO₃, 14, revealed low stability in solution for a long time. The new ligands (S)-2–(S)-5 were tested in the palladium-catalyzed enantioselective substitution of (1,3-diphenyl-1,2-propenyl)acetate by dimethylmalonate. The precatalyst [Pd(η³-C₃H₅)((S)-2)]CF₃SO₃ afforded the allyl substituted product in good yield (95%) and acceptable enantioselectivities (71% e.e. in the S form). A similar result was achieved with the precatalyst [Pd(η³-C₃H₅)((S)-3)]CF₃SO₃. The nucleophilic attack of the malonate occurred preferentially at allylic carbon far from the binaphthalene moiety, namely trans to the phosphite group. When the complexes containing ligands (S)-4 and (S)-5 were used as precatalysts, the product was obtained as a racemic mixture in high yield. The number of the configurational isomers of the Pd-allyl intermediates present in solution in the allylic alkylation and the relative concentrations are considered a determining factor for the enantioselectivity of the process.     

Asymmetric nitrogen−35 : Structure and properties of l(s)-α-carboxyethyl-3, 3-bis(trifluoromethyl)diaziridine and its derivatives

A second-kind asymmetric transformation involving N-atom inversion has been observed at 20° for 1(S) - α - carboxyethyl - 3,3 - bis(trifluoromethyl)diaziridine 1 and its methyl ester 2. X-Ray data for the diastereomer (1S, 2S, α-S), 1A (which is thermodynamically preferred in the crystalline phase), ¹H NMR spectra of ethyl ester 3-¹⁵N(1) and 3-¹⁵N(2), CD spectra of 1A,B, 2A,B, potassium salt 4A,B and semiempirical calculations (MINDO/3 and INDO) for 1A, show that the stereospecificity of crystallization of the diastereomer A is due to the higher energy of the crystal lattice of the diastereomer (1R, 2R, α-S), 1B because of hindered charge compensation as well as to the hindrance by the CF₃, groups to intermolecular H-bonds. According to semiempirical calculations, the stability of 3,3 - bis(trifluoromethyl) - diaziridines (TFD) to the action ofel w-orbital energies and depolarization of the C-N bonds due to hyperconjugation and the inductive effect of the CF₃,-groups. The steric effect of these groups is the reason of the low configurational stability of TFD compared with the 3,3-dimethyl analogues.     

Stereodivergent synthesis of novel chiral C2-symmetric bis-trifluoromethyl-2-oxazolidinones

A simplified effective synthetic process is described for the diastereoselective synthesis of the chiral C₂-symmetric CF₃-ureas (R,R)-15 and (S,S)-15 from (S)-α-phenylethylamine, glyoxal and CF₃I.     

EPR studies on regio-selective H-abstraction by “magic blue” reagent from polymers

The radical reactions of polyolefin and olefin copolymers (4-9), polydienes and diene coplymers (10-15), and polysiloxane (16) with “magic blue” reagent containing H-abstracting agent-bis{perfluoro-1-[1-(2-fluorosulfonyl)ethoxy]ethyl}nitroxide [FSO₂CF₂CF₂OCF(CF₃)]₂N(O) (2)and spin trap-perfluoro-1-nitroso-[1-(2-fluoro-sulfonyl)ethoxy]ethane FSO₂CF₂CF₂OCF(CF₃)NO (3) were studied by EPR detection of the spin adducts of the corresponding polymeric radicals generated in the H-abstraction step to the spin trap 3, namely, the nitroxides FSO₂CF₂CF₂OCF(CF₃)N(O) (polymer-H) 17-29. EPR studies have provided information about the regio-selectivity of H-abstraction, the subsequent radical steps followed H-abstraction and grounded a possibility of employing “magic blue” reagent in polymer modification via H-abstraction-initiated grafting polymerization.     

Structural diversity in the self-assembly of Ag(I) complexes containing 2-amino-5-halopyrimidine

A series of Ag(I) complexes containing the 2-amino-5-halopyrimidine ligands have been synthesized and their structures characterized by X-ray crystallography. The isomorphous complexes Ag(L-Cl)₂(CF₃SO₃) (L-Cl = 2-amino-5-chloropyrimidine), 1, and Ag(L-Br)₂(CF₃SO₃) (L-Br = 2-amino-5-bromopyrimidine), 2, are mononuclear, while [Ag(L-Br)(CF₃SO₃)]₆·6C₄H₁₀O, 3, and [Ag(L-I)(CF₃SO₃)]₆ (L-I = 2-amino-5-iodopyrimidine), 4, show cyclic self-assembly of six Ag(Ι) atoms and six L-X ligands, resulting in 24-membered metallocycles. The complex [Ag(L-I)(CF₃SO₃)]_∞, 5, forms 1D zigzag chains which are linked through C-I?Ag and Ag?O interactions to form a 3D structure. The tetranuclear complexes [Ag(L-X)(NO₃)]₄ [X = Cl, 6; Br, 7] form 16-membered metallocycles, while [Ag(L-X)(ClO₄)]_∞ [X = Cl, 8; Br, 9] exhibit helical chains. The different structure of 5 from 1 and 2 appears to be due to the stronger nucleophilic character of the iodine atom. In these complexes, the relatively smaller NO₃⁻ anions lead to the formation of tetranuclear metallocycles and the larger CF₃SO₃⁻ anions support the hexanuclear metallocycles, whereas the ClO₄⁻ anions induce the helical chains.     

Fluorous modification of 2,2′-bipyridine

A series of 2,2′-bipyridines featuring fluorinated alkyl groups [(CH₂)₃(CF₂)_xCF₃: x = 0, (1); 5, (2); 7, (3); 9 (4)] appended in the 4 and 4′ positions have been prepared. 1-4 were characterized by spectroscopy and physical methods including partition coefficient (biphase: perfluoromethylcyclohexane/toluene) and cyclic voltammetry (THF). Ab-initio calculations of vertical ionization potentials (VIPs) for 1-4 confirm the insulating role of the methylene spacers as the electrochemical reduction potentials of 1-4 are almost identical to that of 2,2′-bipyridine. Calculations for (CH₂)_nCF₃ derivatives (n = 0-10) describe a limit for impact of the CF₃ group through 9-10 methylenes. From both physical and theoretical data fluorinated alkyl groups of the formula (CH₂)₃(CF₂)_xCF₃ [x = 0-9] are inductively equivalent to a hydrogen substituent when appended to the bipyridine moiety.     

Substituted pyridine coordinated N,N-trans and N,N-cis cyclopalladated complexes of (S)-4-tert-butyl-2-phenyl-2-oxazoline: Crystal structures, spectral study and catalysis of the decomposition of PS pesticides

Three pyridine coordinated cyclopalladated complexes: (S)-chloro{2-[2-(4-tert-butyl)oxazolinyl]phenyl-C,N}(4-R-pyridine)palladium(II) (R = H, 2; R = CF₃, 3; R = NMe₂, 4), have been synthesized and structurally characterized. While the crystal structure shows that 2 has a normal N,N-trans-conformation in the coordination sphere of palladium(II), 3 and 4 exhibit uncommon N,N-cis-conformations. From ¹H NMR measurements, the major coordination isomer in deuterated chloroform solution is N,N-trans configuration for three palladacycles. It was found that the three complexes catalyze effectively the methanolysis of the PS pesticides including chiral thiophosphates but show different activity depending on the substituents of co-coordinated pyridine ring in 2–4.     

Single-, double- and triple-bridged derivatives of cyclotriphosphazenes with an octafluorohexane-1,6-diol

Reaction of hexachlorocyclotriphosphazene, N₃P₃Cl₆ (1), with the sodium derivative of the fluorinated diol, 2,2,3,3,4,4,5,5-octafluorohexane-1,6-diol, (2), in THF solution at room temperature afforded five products, whose structures have been characterised by ¹H, ¹⁹F and ³¹P NMR spectroscopy: the mono-ansa compound N₃P₃Cl₄[OCH₂(CF₂)₄CH₂O] (3); the single-bridged compound N₃P₃Cl₅[OCH₂(CF₂)₄CH₂O]N₃P₃Cl₅ (4), two double-bridged compounds N₃P₃Cl₄(OCH₂(CF₂)₄CH₂O)₂N₃P₃Cl₄, (5-anti, 5-syn) and the triple-bridged compound N₃P₃Cl₃(OCH₂(CF₂)₄CH₂O)₃N₃P₃Cl₃ (6). X-ray crystallographic studies confirmed the structures of the ansa compound (3), the double-bridged compound (5-anti) and the first example of a triple-bridged cyclotriphosphazene derivative (6). The results were also compared with those for reactions of (1) with analogous fluorinated shorter diols (1,4-butane- and 1,5-pentane-diols). It is found that on increasing the chain length of the diol, there is a decrease in the relative proportion of intramolecular reactions giving spiro and ansa derivatives and an increase in the amount of bridged cyclophosphazene derivatives via intermolecular reactions.     

Cytotoxic half-sandwich rhodium(III) complexes: Polypyridyl ligand influence on their DNA binding properties and cellular uptake

The DNA binding of polypyridyl (pp) (η⁵-C₅Me₅)Rh^III complexes of the types [(η⁵-C₅Me₅)RhCl(pp)](CF₃SO₃) (2-6) (pp = bpy, phen, dpq, dppz, dppn), [(η⁵-C₅Me₅)Rh{(Me₂N)₂CS}(pp)](CF₃SO₃)₂ (7-9) (pp = dpq, dppz, dppn) and [(η⁵-C₅Me₅)Rh(L)(pp)](CF₃SO₃) (10) (L = C₆H₅S⁻) and (11) (L = C₁₀H₇S⁻) has been studied by UV/Vis spectroscopy, circular dichroismus and viscosity measurements. Complexes 3-11 are cytotoxic towards the human MCF-7 breast and HT-29 colon cancer cell lines and exhibit IC₅₀ values in the range 0.56-10.7 μM. Stable intercalative binding into CT-DNA is indicated for the dpq and dppz complexes by large increases ΔT_m of 6-12 °C in the DNA thermal denaturation temperature for r = [complex]/[DNA] = 0.1 and by induced CD bands and large viscosity increases. In contrast, significant DNA lengthening is not observed after incubation of the biopolymer with the dppn complexes 2 and 9 at molar ratios of r < 0.08. Pronounced hypochromic shifts for the π-π^∗ transitions of the dppn ligands in the range 320-425 nm indicate the possible presence of surface stacking. The in vitro cytotoxicities of the chloro complexes 4-6 and the (Me₂N)₂CS complexes 7-9 are dependent on the size of the polypyridyl ligand with IC₅₀ values decreasing in the order dpq > dppz > dppn. For instance, IC₅₀ values of 5.3, 1.5 and 0.91 μM were determined for 7-9 against MCF-7 cells. Rapid Cl⁻/H₂O exchange leads the formation of aqua dications for 4-6, whose levels of cellular uptake and cytotoxicities are similar to those established for 7-9. Intramolecular interactions between the aromatic thiolate and dppz ligands of 10 and 11 prevent significant DNA intercalation. X-ray structural determinations have been performed for 2-7 and 11.     

Silver(I) and mercury(II) complexes with N,N′-bis(acetylacetone)-1R,2R-diaminocyclohexane ligands exhibiting three different coordination modes

Treatment of AgNO₃ with one equiv. of N,N′-bis(acetylacetone)-1R,2R-diaminocyclohexane (L) afforded a mononuclear complex [Ag(η²-L)NO₃] (1) in which the central silver(I) atom adopts a distorted trigonal planar geometry by coordinating two carbon atoms of the methane moieties of the ligand and one oxygen atom of the NO₃^? group. Interaction of CF₃COOAg with one equiv. of L produced a one-dimensional coordination polymer [Ag₂(μ-L)(CF₃CO₂)₂]_n (2). Each silver(I) in 2 exhibits highly distorted square planar coordination geometry that connects one oxygen atom of L and one neighboring Ag atom with the Ag?Ag interactions. Reaction of HgCl₂ with one equiv. of L resulted in the formation of one-dimensional [{Hg(μ-Cl)Cl}₂(μ-η¹-L)]_n (3) with a C-coordinated dinuclear mercury(II) chloride moiety being linked by L.     

Accelerated Interfacial Charge Transfer in Br-Gradient MAPbI3-xBrx Perovskite Thin Films?

Mixed halide perovskites (MHPs) are a class of semiconductor materials with great promise for many optoelectronic applications due to their outstanding photophysical properties. Understanding and tailoring the photogenerated carrier dynamics is essential for further improvement of perovskite performance. Herein, we report a study about the carrier transport and interfacial charge transfer dynamics in Br-gradient MAPbI_3-xBr_x perovskite thin films prepared by surface ion-exchange method. Driven by the bandgap gradient in MAPbI_3-xBr_x films, the accelerated internal hole transport and enhanced interfacial extraction efficiency were both observed. Meanwhile, the interfacial electron transfer was also found to be evidently facilitated due to the surface modification during post-treatment. Our findings suggest the possibility of simultaneous acceleration of interfacial electron and hole transfer processes in halide perovskite films via surface post-treatment technique, which is of great importance in further improving the power conversion efficiency of perovskite solar cells.     

Synthesis and structural characterisation of gallium and indium fluoroalkoxide ‘ate’ complexes

The treatment of InCl₃ with MOCH(CF₃)₂ (M = Li, Na, K) in a 1:6 stoichiometry, followed by recrystallisation results in the formation of the bimetallic “ate” complexes [Na₃In(OCH(CF₃)₂)₆(THF)₃] (2) and [Li₃In(OCH(CF₃)₂)₆(THF)₃] (5) from hexane, and [K₃In(OCH(CF₃)₂)₆]_n (4) from a THF and toluene mixture. If a 1:3 stoichiometry is used chloride containing compounds [Na₂InCl(OCH(CF₃)₂)₄(THF)₄] (1) and [KInCl₂ (OCH(CF₃)₂)₂(THF)₃]_n · THF (3) are obtained on recrystallisation from hexane. Treatment of GaCl₃ with 6 equivalents of LiOC(CH₃)₂CF₃ gives [LiGa(OC(CH₃)₂CF₃)₄(THF)₂] (6) on recrystallisation from hexane. The protolysis reaction between In(N(SiMe₃)₂)₃, formed in situ from (Me₃Si)₂NH, ⁿBuLi and Incl₃, and HOCH(CH₃)CF₃ results in isolation of [LiIn(OCH(CH₃)CF₃)₃Bu]₂ (7) from hexane. The structures of 2, 4, and 5 all contain the tetranuclear core InO₆M₃. Compounds 1 and 3 have residual chloride; 1 is a trinuclear species with two THF ligands per Na, while 3 is a linear polymer. Compound 6 has a GaO₂Li four-membered parallelogram at its core. Complex 7 has a tetranuclear In₂O₆Li₂ core and an unexpected ⁿBu group on the In atoms. The coordination spheres of the alkali metals in 1-6 include solvated THF while 1-5 display additional close M?F interactions.     

氧化钼-二氧化钛复合膜的可见光致变色性能研究

采用溶胶凝胶法制备了一系列氧化钼-二氧化钛纳米复合物, 用柠檬酸作分散剂, 将得到的纳米复合物粉末分散成溶胶, 涂膜制备了具有可见光变色性能的均匀透明的光致变色(λ≥420 nm)复合膜. 通过红外、XPS、ESR测定表明, 在氧化钼、二氧化钛复合界面上生成了Mo—O—Ti键, 此键的存在是该复合膜具有可见光致变色响应的内在原因. 在可见光的照射下, 电子从二氧化钛的价带经由Mo—O—Ti键, 被激发到氧化钼的导带上. 研究了光致变色过程的动力学, 发现光致变色反应的速率取决于膜中复合物的摩尔比([MoO₃]/[TiO₂])以及电荷转移能量(CTE).     

N-Trifyl substituted 1,4-diheterocyclohexanes—stereodynamics and the Perlin effect

The stereodynamic behaviour of 1-(trifluoromethylsulfonyl)piperidine 1, 4-(trifluoromethylsulfonyl)morpholine 2, 1,4-bis(trifluoromethylsulfonyl)piperazine 3 and 4-(trifluoromethylsulfonyl)thiomorpholine 1,1-dioxide 4 was studied by low-temperature ¹H, ¹³C and ¹⁹F NMR spectroscopies. In acetone solution, compounds 1, 2 and 4 were found to exist as mixtures of two conformers in the ratio of 4:1, 4:1 and 8:1, respectively, differing by orientation of the CF₃ group with respect to the ring. Compound 3 exists as a mixture of three conformers in the ratio of 3:28:69 also differing by the orientation of the two CF₃ groups. Unlike the previously studied N-trifyl substituted 1,3,5-triheterocyclohexanes, the preferred conformers of compound 1 and of 1,4-diheterocyclohexanes 2-4 are those with the CF₃ group directed outward from the ring, which is caused by intramolecular interactions of the oxygen atoms of the CF₃SO₂N groups with the equatorial hydrogens in the α-position. B3LYP/6-311+G(d,p) calculations of the energy, geometry and NMR parameters corroborate the experimental data. The calculated Perlin effects for all conformers of compounds 1-4 as well as those measured for the major conformers of compounds 3 and 4 were analyzed by the use of the NBO analysis.     

Zur Reaktion von Metall-koordinierten Kohlenmonoxid mit Yliden XXII. Bis(diphenylphosphino)methanid-Eisen-Komplexe Cp(L)Fe(Ph2PCHPPh2) (L = CO,Me3P)

The reaction of [Cp(CO)(dppm)Fe]BF₄ (1a) with the phosphorus ylide Me₃PCH₂ yields the novel bis(phosphino)methanideiron complex Cp(CO)Fe(Ph₂PCHPPh₂) (2), which upon photolysis in the presnece of Me₃P is converted into Cp(Me₃P)Fe(Ph₂PCHPPh₂ (3). Reaction of 2 with MeOSO₂CF₃ gives a mixture of the iron salts [(Cp(CO)Fe(Ph₂PCR(R′)PPh₂)]CF₃SO₃ (R = R′ = H (1b), R = R′ = Me (6) and R = H, R′ = Me (syn/anti-4)).     

Layer-by-layer chemical deposition technique for thin film assembly of deposited nano-sized magnesium(II)-5,7-dinitro-8-hydroxyquinolate: Characterization and spectral-optical-electrical properties

Layer-by-layer (LBL) chemical deposition technique was implemented as a low cost and efficient methodology for rapid synthesis and assembly of deposited thin films of nano-sized magnesium(II)-5,7-dinitro-8-hydroxyquinolate complex, Mg[((NO₂)₂-8HQ)₂]. The stoichiometry of deposited nano-sized complex was characterized as a 1:2 ratio based on metal to ligand without contribution of the nitro-group. Further structural characterization and identification were also monitored by using Fourier Transform infrared spectroscopy (FT-IR) in order to confirm the possible mode of bonding in the deposited nano-sized Mg[((NO₂)₂-8HQ)₂] complex. Thermal gravimetric analysis (TGA) of the ligand and complex were studied and compared to evaluate the possible incorporated thermal stability characteristics. Surface imaging of assembled thin film was performed by using scanning electron microscopy (SEM) to confirm high homogeneity in surface particles distribution with average particle size in the range of 30-50 nm. The absorption spectrum of Mg[((NO₂)₂-8HQ)₂] thin film was recorded in the spectral region 250-1000 nm. The optical transmission and reflection spectra of the films have been recorded within the wavelength range 250-2500 nm. The optical parameters of the films, such as absorption index, α, refractive index, n, band gap, E_g, dielectric constants, ε₁ and ε₂ and dissipation factor, tan δ, have been also determined. Two activation energies were determined from the temperature dependence of the dark electrical conductivity. Hopping conduction parameters of Mg[((NO₂)₂-8HQ)₂] have been calculated by employing the variable range hopping model.     

A model for charge transport in semicrystalline polymer thin films

A model for simulating the charge transport properties of semicrystalline polymer (SCrP) using Monte Carlo simulation is reinvented. The model is validated by reproducing the experimentally observed field and temperature dependence of mobility in Poly(3‐hexylthiophene‐2,5‐diyl) (P3HT) thin films. This study also provides a new physical insight to the origin of much debated negative field dependence of mobility (NFDM) observed at low electric field strengths in P3HT thin films. The observed NFDM, which is not explainable with the mechanisms proposed earlier, is attributed to the weak dependence of transit time on the applied electric field strengths. In the semicrystalline films, the charge transport takes place mostly through the crystalline regions, in which the charge transport is weakly dependent on the strength of the applied electric field. In addition, a possible explanation for the origin of Arrhenius temperature dependence of mobility (lnμ ∝ 1/T) commonly observed in SCrP thin films is also proposed. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 137–141