Luminescent Complexes of Europium (III) with 2-(Phenylethynyl)-1,10-phenanthroline: The Role of the Counterions

New antenna ligand, 2-(phenylethynyl)-1,10-phenanthroline (PEP), and its luminescent Eu(III) complexes, Eu(PEP)2Cl3 and Eu(PEP)2(NO3)3, are synthesized and characterized. The synthetic procedure applied is based on reacting of europium salts with ligand in hot acetonitrile solutions in molar ratio 1 to 2. The structure of the complexes is refined by X-ray diffraction based on the single crystals obtained. The compounds [Eu(PEP)2Cl3]∙2CH3CN and [Eu(PEP)2(NO3)3]∙2CH3CN crystalize in monoclinic space group P21/n and P21/c, respectively, with two acetonitrile solvent molecules. Intra- and inter-ligand π-π stacking interactions are present in solid stat and are realized between the phenanthroline moieties, as well as between the substituents and the phenanthroline units. The optical properties of the complexes are investigated in solid state, acetonitrile and dichloromethane solution. Both compounds exhibit bright red luminescence caused by the organic ligand acting as antenna for sensitization of Eu (III) emission. The newly designed complexes differ in counter ions in the inner coordination sphere, which allows exploring their influence on the stability, molecular and supramolecular structure, fluorescent properties and symmetry of the Eu (III) ion. In addition, molecular simulations are performed in order to explain the observed experimental behavior of the complexes. The discovered structure-properties relationships give insight on the role of the counter ions in the molecular design of new Eu (III) based luminescent materials.

Theoretical Investigation of Excited-State Intramolecular Double-Proton Transfer Mechanism of Substituent Modified 1, 3-Bis (2-pyridylimino)-4,7-dihydroxyisoindole in Dichloromethane Solution

In this paper, density functional theory (DFT) and time-dependent DFT (TDDFT) methods were used to investigate substituent effects and excited-state intramolecular double-proton transfer (ESIDPT) in 1, 3-bis (2-pyridylimino)-4, 7-dihydroxyisoindole (BPI–OH) and its derivatives. The results of a systematic study of the substituent effects of electron-withdrawing groups (F, Cl and Br) on the adjacent sites of the benzene ring were used to regulate the photophysical properties of the molecules and the dynamics of the proton-transfer process. Geometric structure comparisons and infrared (IR) spectroscopic analysis confirmed that strengthening of the intramolecular hydrogen bond in the first excited state (S1) facilitated proton transfer. Functional analysis of the reduced density gradient confirmed these conclusions. Double-proton transfer in BPI–OH is considered to occur in two steps, i.e., BPI–OH (N) [Formula: see text] BPI–OH (T1) [Formula: see text] BPI–OH (T2), in the ground state (S0) and the S1 state. The potential-energy curves (PECs) for two-step proton transfer were scanned for both the S0 and S1 states to clarify the mechanisms and pathways of proton transfer. The stepwise path in which two protons are consecutively transferred has a low energy barrier and is more rational and favorable. This study shows that the presence or absence of coordinating groups, and the type of coordinating group, affect the hydrogen-bond strength. A coordinating group enhances hydrogen-bond formation, i.e., it promotes excited-state intramolecular proton transfer (ESIPT).

Synthesis of 3,3′- Di-indolylmethanes under mild conditions by Microwave Irradiation Mediated Reactions of Indoles with C, N-Diaryl nitrones

3,3′-Di-indolylmethane derivatives are important biologically active compounds possessing anti-cancer properties. Hence, development of synthetic routes to these are of great interest to organic chemists. In the present communication we report a high-yield method using mild reaction conditions and short reaction times for the synthesis of 3,3′-di-indolylmethane derivatives. The method involved reactions of indole and substituted indoles with C,N-disubstituted nitrones in the presence of acid catalysts, with the utilisation of microwave irradiation techniques. Reactions of indole, 2-methyl indole and 2-phenyl indole were performed with ten different C,N-diaryl- and C-aryl-N-methyl- nitrones in dichloromethane solution in the absence and presence of acid catalysts, viz. ytterbium triflate, p-toluene sulphonic acid and Montmorillonite clay K-10. Reaction times varied between 2 to 18 minutes. In general, yields of the catalysed reactions were above 75%. The products were characterised spectroscopically, including two-dimensional NMR studies. The microwave irradiation technique enhanced reaction rates by a significant amount. Ytterbium triflate proved to be the best catalyst, giving clean reactions, without formation of by-products, in high yields. The structure and conformation of 3,3′-di-indolyl-phenylmethane were computed. GRAPHICAL ABSTRACT: We report a high-yield method using mild reaction conditions and short reaction times for the synthesis of 3,3′-di-indolylmethane derivatives, involving reactions of indole and substituted indoles with C, N-disubstituted nitrones in the presence of acid catalysts using microwave irradiation.

Theoretical Investigation of Excited-State Intramolecular Double-Proton Transfer Mechanism of Substituent Modified 1, 3-Bis (2-pyridylimino)-4,7-dihydroxyisoindole in Dichloromethane Solution

Density functional theory (DFT) and time-dependent DFT (TDDFT) methods were used to investigate substituent effects and excited-state intramolecular double-proton transfer in 1, 3-bis (2-pyridylimino)-4, 7-dihydroxyisoindole (BPI-OH) and its derivatives. The results of a systematic study of the substituent effects of electron-withdrawing groups (F, Cl, and Br) on the adjacent sites of the benzene ring were used to regulate the photophysical properties of the molecules and the dynamics of the proton-transfer process. Geometric structure comparisons and infrared spectroscopic analysis confirmed that strengthening of the intramolecular hydrogen bond in the first excited state (S1) facilitated proton transfer. Functional analysis of the reduction density gradient confirmed these conclusions. Double-proton transfer in BPI-OH is considered to occur in two steps, i.e., BPI-OH (N) →BPI-OH (T1) →BPI-OH (T2), in the ground state (S0) and the S1 state. The potential-energy curves for two-step proton transfer were scanned for both the S0 and S1 states to clarify the mechanisms and pathways of proton transfer. The stepwise path in which two protons are consecutively transferred has a low energy barrier and is more rational and favorable. This study shows that the presence or absence of coordinating groups, and the type of coordinating group, affect the hydrogen-bond strength. A coordinating group enhances hydrogen-bond formation, i.e., it promotes excited-state intramolecular proton transfer.

1,1′-Bis(diphenylphosphino)ferrocene Platinum(II) Complexes as a Route to Functionalized Multiporphyrin Systems

In this study, the cationic complex [PtMe(Me2SO)(dppf)]CF3SO3 (PtFc) (dppf = 1,1′-bis(diphenylphosphino)ferrocene) was exploited as a precursor to functionalize the multi-chromophoric system hexakis(pyridyl-porphyrinato)benzene (1). The final adduct [PtFc]18-1, containing eighteen platinum(II) organometallic [PtMe(dppf)] fragments, was prepared and characterized through UV/Vis absorption, 31P{1H}-NMR spectroscopy, and fluorescence emission. UV/vis and fluorescence titrations confirmed the coordination between the platinum(II) center and all the pyridyl moieties of the peripheral substituent groups of the porphyrin. The drop casting of diluted dichloromethane solution of [PtFc]18-1 onto a glass surface afford micrometer-sized emissive porphyrin rings.

Fluorescence quenching of methanol-soluble polypyrimidine by aluminum ion

The different proportion methylpyrimidine ring copolymers has been synthesized and characterized by 1HNMR, 13CNMR and FT-IR spectrum. The detection limit of P80 for Al3+ ions of 7.94 × 10–8 M at the dichloromethane solution. The binding constant (Kb) between copolymers and with Al3+ was 1.10 × 104 M–1. The EDS analysis and XPS spectroscopy can expose that the copolymer and Al3+ had been coordination with each other. The neutral polymers with good recovery properties can be used as sensor detect Al3+ in the organic solvent. The methanol-soluble polymer has been synthesized from methylpyrimidine ring copolymers, and investigated acidochromic properties and found that the acidochromic property of the polymer was retained after quaternization, but cannot detect Al3+ in the methanol (MeOH). The methanol-soluble polymers using environment-friendly solvents such as methanol can be used in detect H+ in the methanol.

Co-crystal structure, Hirshfeld surface analysis and DFT studies of 3,4-ethylenedioxythiophene solvated bis[1,3-bis(pentafluorophenyl)propane-1,3-dionato]copper(II)

The title complex, Cu(L)2 or [Cu(C15HF10O2)2], comprised of one copper ion and two fully fluorinated ligands (L −), was crystallized with 3,4-ethylenedioxythiophene (EDOT, C6H6O2S) as a guest molecule to give in a dichloromethane solution a unique co-crystal, Cu(L)2·3C6H6O2S. In the crystal, the oxygen of one guest molecule, EDOT-1, is coordinated to the metal to give an alternate linear arrangement, and the π-planes of the others, EDOT-2 and EDOT-3, interact weakly with the pentafluorophenyl groups of the complex through arene–perfluoroarene interactions. Head-to-tail columnar and head-to-head dimeric arrangements are observed for EDOT-2 and EDOT-3, respectively, in the crystal. The Hirshfeld surface analysis indicated that the most important contributions for the crystal packing are from the F...F (20.4%), F...H/H...F (24.5%) and F...C/C...F (9.6%) interactions. The density functional theory (DFT) optimized structure at the ωB97X-D 6–31G* level was compared with the experimentally determined molecular structure in the solid state.

Pd/C-CATALISED HYDROGENIZATION OF METHYL PYRROLE-3-CARBOXYLATES IN THE DIASTEREOSELECTIVE SYNTHESIS OF α-SUBSTITUTED β-PROLINES

The analysis of synthetic and biological importance of α-substituted β-prolines was conducted. Methods of synthesis of β-prolines and their esters, based on both intra- and intermolecular reactions of formation of functionalized pyrrolidinic cycle, as well as catalytic reduction of corresponding 2,3-substituted pyrroles and their dihydro derivatives, were systematized. The necessity of the hydrogenation process improvement of 2,3-di-substituted pyrroles using cheap catalysts was justified. The approach to α-substituted β-prolines (2-substituted pyrrolidine-3-carboxylic acids) was pro-posed, the first stage of which is N-Boc-protection of 2-substituted pyrrolidine-3-carboxylates with di-tert-butyl dicarbonate (Boc-anhydride) in the dichloromethane solution at the room temperature in presence of catalytic amounts of N,N-dime-thylaminopyridine. Obtained derivatives were subjected to hydrogenation in the autoclave at 45 atm. at 40 oC for 20 hours in presence of 10 % Pd/C catalyst. It was found, that reaction at such conditions proceeds with the full conversion of starting compounds and demonstrates high stereoselec-tivity and leads to the mixture of diastereomeric N-Boc-protected pyrrolidine-3-carboxylates of cis- and trans-configurations with corresponding contents of 84–87 % and 13–16 % according to NMR 1Н and chromato-mass spectra. The mild hydrolysis of isolated reaction mixtures in the water solution of lithium hydroxide followed by neutrali-zation and N-Boc-deprotection with 15 % hydrochloric acid allows isolating pure major diaste-reomers of α-substituted β-prolines with 69–74 % yields. Their trans-configuration was reliably confirmed by NMR 1Н spectroscopy using the NOESY experiment.

Linear One-Dimensional Coordination Polymers Constructed by Dirhodium Paddlewheel and Tetracyanido-Metallate Building Blocks

In this article, we describe the preparation of anionic heteronuclear one-dimensional coordination polymers made by dirhodium paddlewheels and tetracyanido-metallatate building blocks. A series of complexes of (PPh4)2n[{Rh2(µ-O2CCH3)4}{M(CN)4}]n (M = Ni (1), Pd (2), Pt (3)) formulae were obtained by reaction of [Rh2(μ-O2CCH3)4] with (PPh4)2[M(CN)4] in a 1:1 or 2:1 ratio. Crystals of 1−3 suitable for single crystal X-ray diffraction were grown by slow diffusion of a dichloromethane solution of the dirhodium complex into a chloroform solution of the corresponding tetracyanido–metallatate salt. Compounds 1 and 2 are isostructural and crystallize in the triclinic P-1 space group, while compound 3 crystallizes in the monoclinic P21/n space group. A detailed description of the structures is presented, including the analysis of the packing of anionic chains and PPh4+ cations.