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The introduction of an electron-donating triphenylamine motive into a 2,2′,6′,2′′-terpyridine (terpy) moiety, a cornerstone molecular unit in coordination chemistry, opens new ways for a rational design of photophysical properties of organic and inorganic compounds. A push-pull compound, 4′-(4-(di(4-tert-butylphenyl)amine)phenyl)-2,2′,6′,2′′-terpyridine (tBuTPAterpy), was thoroughly investigated with the use of steady-state and time-resolved spectroscopies and Density Functional Theory (DFT) calculations. Our results demonstrate that solvent parameters have an enormous influence on the optical properties of this molecule, acting as knobs for external control of its photophysics. The Intramolecular Charge Transfer (ICT) process introduces a remarkable solvent polarity effect on the emission spectra without affecting the lowest absorption band, as confirmed by DFT simulations, including solvation effects. The calculations ascribe the lowest absorption transitions to two singlet ICT excited states, S1 and S2, with S1 having several orders of magnitude higher oscillator strength than the "dark" S2 state. Temperature and viscosity investigations suggest the existence of two emitting excited states with different structural conformations. The phosphorescence emission band observed at 77 K is assigned to a localized 3terpy state. Finally, protonation studies show that tBuTPAterpy undergoes a reversible process, making it a promising probe of the pH level in the context of acidity determination. [ABSTRACT FROM AUTHOR]

The structure–property correlations and control of electronic excited states in transition metal complexes (TMCs) are of high significance for TMC-based functional material development. Within these studies, a series of Re(I) carbonyl complexes with aryl-substituted 2,6-di(thiazol-2-yl)pyridines (Arn-dtpy) was synthesized, and their ground- and excited-state properties were investigated. A number of condensed aromatic rings, which function as the linking mode of the aryl substituent, play a fundamental role in controlling photophysics of the resulting [ReCl(CO)3(Arn-dtpy-κ2N)]. Photoexcitation of [ReCl(CO)3(Arn-dtpy-κ2N)] with 1-naphthyl-, 2-naphthyl-, 9-phenanthrenyl leads to the population of 3MLCT. The lowest triplet state of Re(I) chromophores bearing 9-anthryl, 2-anthryl, 1-pyrenyl groups is ligand localized. The rhenium(I) complex with appended 1-pyrenyl group features long-lived room temperature emission attributed to the equilibrium between 3MLCT and 3IL/3ILCT. The excited-state dynamics in complexes [ReCl(CO)3(9-anthryl-dtpy-κ2N)] and [ReCl(CO)3(2-anthryl-dtpy-κ2N)] is strongly dependent on the electronic coupling between anthracene and {ReCl(CO)3(dtpy-κ2N)}. Less steric hindrance between the chromophores in [ReCl(CO)3(2-anthryl-dtpy-κ2N)] is responsible for the faster formation of 3IL/3ILCT and larger contribution of 3ILCTanthracene→dtpy in relation to the isomeric complex [ReCl(CO)3(9-anthryl-dtpy-κ2N)]. In agreement with stronger electronic communication between the aryl and Re(I) coordination centre, [ReCl(CO)3(2-anthryl-dtpy-κ2N)] displays room-temperature emission contributed to by 3MLCT and 3ILanthracene/3ILCTanthracene→dtpy phosphorescence. The latter presents rarely observed phenomena in luminescent metal complexes. [ABSTRACT FROM AUTHOR]

A series of iridium(III) triimine complexes incorporating 2,2′:6′,2″-terpyridine (terpy) and 2,6-bis(thiazol-2-yl)pyridine (dtpy) derivatives were successfully designed and synthesized to investigate the impact of the peripheral rings (pyridine, thiazole) and substituents (thiophene, bithiophene, EDOT) attached to the triimine skeleton on their photophysical properties. The Ir(III) complexes were fully characterized using IR, 1H, elemental analysis and single crystal X-ray analysis. Their thermal properties were evaluated using TGA measurements. Photoluminescence spectra of [IrCl3L1–6] were investigated in solution at 298 and 77 K. The experimental studies were accompanied by DFT/TDDFT calculations. The photophysical properties of the synthesized triimine ligands and Ir(III) complexes were studied in detail by electronic absorption and emission. In solution, they exhibited photoluminescence quantum yields ranging from 1.27% to 5.30% depending on the chemical structure. The experimental research included DFT/TDDFT calculations. The photophysical properties of the synthesized triimine ligands and Ir(III) complexes were conducted using electronic absorption and emission techniques. In solution, they displayed photoluminescence quantum yields ranging from 1.27% to 5.30% depending on the chemical structure. [ABSTRACT FROM AUTHOR]

The ground- and excited-state properties of three novel complexes [ReCl(CO)3(Ln-κ2N)] bearing 2,2′:6′,2′′-terpyridine, 2,6-di(thiazol-2-yl)pyridine and 2,6-di(pyrazin-2-yl)pyridine functionalized with 9-carbazole attached to the central pyridine ring of the triimine core via phenylene linkage were investigated by spectroscopic and electrochemical methods and were simulated using density functional theory (DFT) and time-dependent DFT. To get a deeper and broader understanding of structure–property relationships, the designed Re(I) carbonyl complexes were compared with previously reported analogous systems – without any groups attached to the phenyl ring and bearing pyrrolidine instead of 9-carbazole. The results indicated that attachment of the N-carbazolyl substituent to the triimine core has less influence on the nature of the triplet excited state of [ReCl(CO)3(Ln-κ2N)] than the pyrrolidine group. Additionally, the impact of the ligand structural modifications on the light emission of the Re(I) complexes under external voltage was preliminarily examined with electroluminescence spectra of diodes containing the synthesized new molecules in an active layer. [ABSTRACT FROM AUTHOR]

The photophysical properties of platinum(II) compounds with 4-(9-anthryl)-2,6-bis(thiazol-2-yl)pyridine (1) and 4-(1-pyrenyl)-2,6-bis(thiazol-2-yl)pyridine (2) were widely investigated. In DMSO and MeCN, the triplet emission of (1) and (2) most probably experiences the solvent-induced exciplex quenching and both complexes exhibit ligand-based fluorescence with maxima in the range of 468–570 nm. In non-coordinating dichloromethane, the emission of (1) and (2) shifts to longer wavelengths, and the lifetimes in microseconds are indicative of phosphorescence. The formation of the triplet excited state was further supported by the observation of singlet oxygen photoluminescence in the near-IR at 1270 nm. To explore the nature of the triplet excited state, the emission properties of (1) and (2) in low temperature glasses were analysed in comparison with those for free ligands and appropriate hydrocarbons, as well as transient absorption spectra were recorded in femtosecond and nanosecond regimes. The studies revealed that the lowest energy triplet state of both complexes is an admixture of 3ILCT and 3(π–π*)aryl character, but the contribution of the 3ILCT state in (1) originating from anthracene to 2,6-bis(thiazol-2-yl)pyridine can be determined as rather negligible. [ABSTRACT FROM AUTHOR]

Three Re(I) carbonyl complexes [ReCl(CO)3(Ln)] bearing 2,2′-bipyridine, 2,2′:6′,2′′-terpyridine, and 1,10-phenanthroline functionalized with diphenylamine/or triphenylamine units (L1–L3) were synthesized to explore the impact of highly electron donating units appended to the imine ligand on the thermal and optoelectronic properties of Re(I) systems. Additionally, for comparison, the ligands L1–3 and parent complexes [ReCl(CO)3(bipy)], [ReCl(CO)3(phen)] and [ReCl(CO)3(terpy-κ2N)] were investigated. The thermal stability was evaluated by differential scanning calorimetry. The ground- and excited-state electronic properties of the Re(I) complexes were studied by cyclic voltammetry and differential pulse voltammetry, absorption and emission spectroscopy, as well as using density-functional theory (DFT). The majority of the compounds form amorphous molecular materials with high glass transition temperatures above 100 °C. Compared to the unsubstituted complexes [ReCl(CO)3(bipy)], [ReCl(CO)3(phen)] and [ReCl(CO)3(terpy-κ2N)], the HOMO–LUMO gap of the corresponding Re(I) systems bearing modified imine ligands is reduced, and the decrease in the value of the ΔEH–L is mainly caused by the increase in HOMO energy level. In relation to the parent complexes, all designed Re(I) carbonyls were found to show enhanced photoluminescence, both in solution and in solid state. The investigated ligands and complexes were also preliminarily tested as luminophores in light emitting diodes with the structures ITO/PEDOT:PSS/compound/Al and ITO/PEDOT:PSS/PVK:PBD:compound/Al. The pronounced effect of the ligand chemical structure on electroluminescence ability was clearly visible. [ABSTRACT FROM AUTHOR]

This is the first comprehensive review of rhenium(I) carbonyl complexes with 2,2′:6′,2″-terpyridine-based ligands (R-terpy)—encompassing their synthesis, molecular features, photophysical behavior, and potential applications. Particular attention has been devoted to demonstrating how the coordination mode of 2,2′:6′,2″-terpyridine (terpy-κ2N and terpy-κ3N), structural modifications of terpy framework (R), and the nature of ancillary ligands (X—mono-negative anion, L—neutral ligand) may tune the photophysical behavior of Re(I) complexes [Re(X/L)(CO)3(R-terpy-κ2N)]0/+ and [Re(X/L)(CO)2(R-terpy-κ3N)]0/+. Our discussion also includes homo- and heteronuclear multicomponent systems with {Re(CO)3(R-terpy-κ2N)} and {Re(CO)2(R-terpy-κ3N)} motifs. The presented structure–property relationships are of high importance for controlling the photoinduced processes in these systems and making further progress in the development of more efficient Re-based luminophores, photosensitizers, and photocatalysts for modern technologies. [ABSTRACT FROM AUTHOR]

[Display omitted] • The relationship between the molecular structure and optical properties of pyrazoline-based push-pull dyes was discussed. • The photoinduced charge/electron transfer process over carbonyl bridge included in π-system was observed. • The thiophene-decorated pyrazoline presents good photovoltaic properties. • The phenyl end capped pyrazoline can be used as a viscosity sensor. • The deactivation pathway is mostly affected by conformational relaxation and back electron transfer process. The manuscript describes the effect of molecular structure on the photophysical and photovoltaic properties of the pyrazoline-based donor-branched-π-system-acceptor compounds decorated with two end groups: phenyl or thiophene. Although the absorption to the first singlet excited state is strongly allowed, the emission quantum yield is low in all studied solvents. This behaviour was explained by the existence of two non-radiative deactivation channels: the back electron transfer process, especially operated in polar solvents, and internal conversion realized as the rotation of flexible rotors (cyano, keto phenyl or thiophene). The feasibility of the photoinduced electron transfer process was corroborated by electrochemical, spectroelectrochemical measurements as well as DFT calculations. DFT calculations also support the existence of multiple conformations in the ground state, which differ from one another in terms of charge distribution and the values of ground state dipole moment. Finally, the mechanism of the singlet excited state deactivation of the studied compounds was determined by ultrafast pump-probe measurements. Our studies revealed that charge/electron transfer process may undergo over carbonyl bridge, included in branched π-system. Moreover, the thiophene decorated pyrazoline is characterized by a better photovoltaic power conversion efficiency, while the phenyl-ended pyrazoline can be applied as a viscosity sensor. [ABSTRACT FROM AUTHOR]

Abstract: Six novel fluoranthene derivatives, namely, three terminally substituted and three bis(fluoranthene) units with fluorene, bithiophene, and carbazole spacers, were obtained through [2+2+2] cycloaddition and characterized completely. Based on the conducted studies, the obtained derivatives can be classified as donor–acceptor (D‐A) and acceptor‐donor‐acceptor (A‐D‐A) systems, in which the fluoranthene unit acts as an electron‐withdrawing unit. The optical results revealed that novel fluoranthene derivatives absorb light in the range λ=236–417 nm, which originates from a π→π* transition within the conjugated system. The compounds exhibit fluorescence that range from deep blue to green, which mainly arises from intramolecular charge transfer (ICT) states. High Stoke shifts and high quantum yields in solution (ϕ=0.22–0.57) and in the solid state (ϕ=0.18–0.44) have been observed for fluoranthene derivatives. All the derivatives display multistep oxidation processes at low potentials. The electronic structure of the presented compounds is additionally supported by time‐dependent DFT computations. [ABSTRACT FROM AUTHOR]

Structural, spectroscopic and electrochemical properties of six complexes [AuCl(L1)](PF6)2·CH3CN (1), [AuCl(L2)](PF6)2 (2), [PtCl(L1)](BPh4)·CH3CN (3), [PtCl(L2)](SO3CF3) (4), [CuCl2(L1)] (5) and [CuCl2(L2)]·CH3CN (6) with modified 2,2′:6′,2′′-terpyridine ligands, 4′-(4-methoxyphenyl)-2,2′:6′,2′′-terpyridine (L1) and 4′-(4-methoxynaphthalen-1-yl)-2,2′:6′,2′′-terpyridine (L2) were thoroughly investigated and a significant role of the substituent (4-methoxyphenyl or 4-methoxynaphthalen-1-yl) and the metal center was demonstrated. The naphthyl-based substituent was found to increase the emission quantum yield of the luminescent Au(iii) and Pt(ii) complexes. Furthermore, the antiproliferative potential of the reported complexes was examined towards human colorectal (HCT116) and ovarian (A2780) carcinoma cell lines as well as towards normal human fibroblasts. The Au(iii) complex 2 and Cu(ii) complex 5 were found to have a higher antiproliferative effect on HCT116 colorectal and A2780 ovarian carcinoma cells when compared with the Pt(ii) complex with the same ligand (4). The order of cytotoxicity in both cell lines is 2 ＞ 6 ＞ 1 ＞ 3 ＞ 4. Complex 2 seems to be more cytotoxic towards HCT116 and A2780 cancer cell lines with IC50 values 300× and 130× higher in normal human fibroblasts compared to the respective cancer cells. The viability loss induced by the complexes agrees with Hoechst 33258 staining and the typical morphological apoptotic characteristics like chromatin condensation and nuclear fragmentation and flow cytometry assay. The induction of apoptosis correlates with the induction of reactive oxygen species (ROS). Fluorescence microscopy analysis indicates that after 3 h of incubation, complexes 1–4 are localized inside HCT116 cells and the high levels of internalization correlate with their cytotoxicity. [ABSTRACT FROM AUTHOR]

Mononuclear coordination compounds of copper(I) – [Cu(PPh 3 ) 2 (picoline)(NO 3 )], zinc(II) – [ZnCl 2 (picoline) 2 ] (picoline=3– and 4–methylpyridine) and polymeric cadmium(II) – [CdCl 2 (β-picoline) 2 ] n were prepared and their luminescence properties in solid state and acetonitrile solutions were determined. Single crystal X-ray crystallography revealed distorted tetrahedral geometry around the central ions of the compounds. The compounds exhibit green photoluminescence in solid state and in acetonitrile solutions. The emission of copper(I) compounds originated from metal-to-ligand charge transfer state combined with nitrato-to-picoline charge transfer state i.e. ( 1 (M+X)LCT). The presence of nitrato ligand in the coordination sphere of copper(I) compounds quenches the emission. Luminescence of zinc(II) and cadmium(II) compounds results from chloride-to-picoline charge transfer state and the quantum efficiency in the case of the polymeric Cd(II) compound reaches 39%. The photoluminescence quantum yields of the mononuclear zinc(II) compounds vary from 10 to 16% depending on the conditions (solid state, solution). [ABSTRACT FROM AUTHOR]

Several 2,6-di(thiazol-2-yl)pyridine (dtpy) derivatives substituted at the 4-position were synthesized, and their structural, photophysical, and electrochemical properties were investigated. The studies proved the attractiveness of this new class of compound as building blocks for materials science, coordination chemistry, and supramolecular chemistry and also revealed the possible tuning of their thermal, photophysical, electrochemical, and electroluminescence properties through the modification of the structure of the substituent. The thermal,photophysical, and electrochemical behavior of the compounds was examined by differential scanning calorimetry (DSC) and for selected compounds by thermogravimetric analysis (TGA), UV/Vis spectroscopy, photoluminescence (PL) spectroscopy, and cyclic voltammetry (CV). Additionally, their selected properties were investigated theoretically by density functional theory (DFT) calculations. The electroluminescence abilities of the synthesized compounds were preliminary tested in host-guest light-emitting diodes. [ABSTRACT FROM AUTHOR]

The p -tolyldiazenido ruthenium [RuCl 2 (CO)(PPh 3 ) 2 (N 2 PhCH 3 )] ( 1 ) and [RuCl 2 (CO)(PPh 3 ) 2 (HPz) 2 ] ( 2 ) and [RuCl 2 (CO)(PPh 3 )(py)] ( 3 ) coordination compounds were synthesized and characterized by IR, 1 H, 13 C, 31 P NMR, electronic absorption and X-ray crystallography. The structural parameters showed the bent coordination mode of N 2 PhCH 3 ligand in complex ( 1 ) but the measured magnetic susceptibility showed a week response to the ac applied magnetic field and a lack of a Curie–Weiss region means diamagnetism. The most spectacular observation concerns the ZFC-FC splitting, however, the product χ · T versus temperature T is revealing none to the anomaly. The reactions of ( 1 ) with pyrazole and pyridine lead to monophosphine complexes so it may be used as a precursor for the synthesis of the new monophosphine carbonyl ruthenium coordination compounds(II). [ABSTRACT FROM AUTHOR]

Abstract: Ruthenium(II) complexes with the general formulas [Ru(H/Cl)(CO)(PPh3)2(L)] and cis/trans-[Ru(PPh3)2(L)2] (L=isoquinoline-1-carboxylate or quinoline-2-carboxylate) were synthesized and characterized by IR, 1H, 13C and 31P NMR, UV–Vis spectroscopy and X-ray crystallography. The experimental studies were completed by quantum chemical calculations, which were used to describe the nature of the interactions between the ligands and the central ion, and the orbital compositions in the frontier electronic structures. Based on a molecular orbital scheme, the calculated results allowed the interpretation of the UV–Vis spectra obtained at an experimental level. The luminescence properties of the complexes were determined. [Copyright &y& Elsevier]

Abstract: The reaction between [RuHCl(CO)(PPh3)3] and 2-methyl-4(5)-nitroimidazole (L) has been performed and the hydride carbonyl ruthenium(II) complex [RuH(CO)(PPh3)2(L)] has been obtained by this reaction, running with deprotonation of the ligand. The molecular structure of the complex has been determined by X-ray crystallography and its spectroscopic characterization has been carried out by IR, 1H, 31P and 13C NMR, UV–Vis spectroscopy. Supported by the DFT computational method, the electronic structure is described in order to explain the absorption and emission spectra obtained experimentally. The luminescence property of the complex has been examined and the quantum yield of the fluorescence has been obtained by a comparative method. The observable fluorescence is related to MLLCT excited states. The imidazole derivative ligand plays a role in the creation of the excited states. [Copyright &y& Elsevier]

The [RuH(CO)(hqxc)(PPh 3 ) 2 ] complex, where hqxc is 3-hydroxy-2-quinoxalinecarboxylate, exhibits strong phosphorescence (quantum yield F = 0.0078) in the solid state giving rise to a significantly Stokes-shifted spectrum (excitation at 484 nm and emission at 687 nm); the lifetime of 6.5 μ s is very long compared with 0.68 ns measured for the free hqxc ligand. [ABSTRACT FROM AUTHOR]

The title complex was synthesized and characterized by IR, NMR and UV-VIS spectroscopy and X-ray crystallography; the electronic structure of the complex was calculated using the density functional theory. [Copyright &y& Elsevier]

{PtCl[4′-(4-NMe 2)-Ph-terpy-κ3N]}BPh 4 ·CH 3 CN was synthesized and its structural, electrochemical and photophysical properties were characterized in comparison to previously described systems of [PtCl(4′-Ph-terpy-κ3N)]+ and [PtCl(4′-NMe 2 -terpy-κ3N)]+. {PtCl[4′-(4-NMe 2)-Ph-terpy-κ3N]}BPh 4 ·CH 3 CN (1) was synthesized and its structural, electrochemical and photophysical properties were characterized in comparison to previously described systems of [PtCl(4′-Ph-terpy-κ3N)]+ and [PtCl(4′-NMe 2 -terpy-κ3N)]+ to determine again the significance of the appropriate design of substituent in case of luminescence behavior of transition metal complex. The molecular formula of compound was confirmed by. X-ray analysis, elemental analysis, FT-IR and NMR studies. The geometries of ground and excited states of compound were also calculated on the basis of Density Functional Theory (DFT) method. The electrochemical properties were elucidated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The electronic absorption spectra of compound (1) in solutions are similar to those in described previously platinum(II) terpyridine coordination compounds. The photoluminescence properties were studied in various media to rationalize effects on emission properties caused by substituent, solvent polarity, concentration of solution and rigidity of media. The studied compound displays enhancement of photoluminescence properties in comparison to [PtCl(terpy-κ3N)]+ system, however its emission lifetime in the regard to [PtCl(4′-Ph-terpy-κ3N)]+ and [PtCl(4′-NMe 2 -terpy-κ3N)]+ is significantly decreased. This suggest the impeded charge transfer from electron-rich NMe 2 group via phenylene bridge to the terpy core due to the unfavorable, inclined geometry of excited state. As a consequence of substituent twisting on the path S 0 → S 1 → T 1 , the interference of 3ILCT and 3MLCT excited state is disturbed favouring the non-radiative deactivation process of {PtCl[4′-(4-NMe 2)-Ph-terpy-κ3N]}BPh 4 ·CH 3 CN. [ABSTRACT FROM AUTHOR]

The copolymerization of ethylene (E) with isoprene (Ip) was performed catalyzed by a symmetrical catalyst exhibiting a silicon bridge [rac-Me 2 Si(2-Me-4-Ph-Ind) 2 ZrCl 2 with the combination of borate/TIBA activator. The effect of cocatalyst, Ip concentration, and polymerization temperature on the activity, molecular weight (Mw), distribution (MWD), comonomer composition, chain structure (regio- and stereoselectivity), and resulting side reactions were logically addressed. Gel-permeation chromatography (GPC) was used to characterize the Mw and polydispersity, while nuclear magnetic resonance (NMR) was employed for the chain structure of the polymers. The catalytic activity was significantly lower by increasing the Ip concentration in the feed, and the isoprene content in resulting polymers was lower under the reaction condition, leading to higher activity. Insertion of isoprene units in polymer structure demonstrates the higher regioselectivity for the 3,4 connections than the 1,4 connections and is expected to be a high-resistance polymer against acids. The MWD presented monomodal even with a higher concentration (1.44 mol/L) and did not appear as low Mw peaks of Ip. The Mw was higher with a broader MWD when purely TIBA was used as a cocatalyst, and it significantly reduced and presented a narrowed MWD with TEA in the cocatalyst. The higher efficiency of the catalyst for the higher insertion of Ip (C=C double bond) effectively modifies the polymer backbone. It is expected to be a promising candidate for easily degradable and favorable solutions for solving environmental problems caused by PE. wastes. [Display omitted] • Environmentally benign methodology reaction conditions (low temperature and pressure) are hallmarks of this approach. • Ethylene α-olefin (linear conjugated diene) copolymerization catalyzed with a symmetrical Single-site homogeneous catalyst. • Ethylene α-olefin (linear conjugated diene) copolymerization catalyzed with a symmetrical Single-site homogeneous catalyst. • The MWD demonstrated monomodal even with a higher concentration of isoprene (1.44 mol/L). • Increased insertion of isoprene may lead to easily degradable and beneficial solutions for PE waste environmental issues. [ABSTRACT FROM AUTHOR]

A series of 2,6-di(thiazol-2-yl)pyridines (dtpy) functionalized at 4-position with 1-naphtyl (1), 2-naphtyl (2), 9-anthryl (3), 2-anthryl (4), 9-phenantryl (5) and 1-pyrenyl (6) groups has been synthesized and thoroughly investigated. The molecular formulas of 1 – 6 were determined by 1H and 13C NMR, elemental analysis and X-Ray analysis (1 , 3 and 5). In the solid state structures, the dtpy framework shows good planarity, while the aryl substituent is significantly inclined to the central pyridine to minimize inter-ring H⋯H repulsions and hydrogen–π-ring steric repulsions. The nature of excited states involved in the photophysical processes has been explored by carrying out absorption and emission UV–Vis studies in solution and solid state, as well as quantum chemical calculations. Large aryl substituents, such as anthryl and pyrenyl, induce a remarkable red-shift of the absorption and emission bands, in agreement with a stronger π-delocalization. For compounds 3 , 4 and 6 , which show a large, positive solvatochromism, the excited states gain significant charge transfer (CT) character. The efficiency of the ICT/TICT state formation was found to depend on solvent polarity and torsional hindrance between the aryl and dtpy moieties. To investigate the impact of torsional hindrance on ICT formation, ultrafast pump–probe measurements were performed for compounds 3 and 4. All the synthesized dtpy were electrochemically active and undergo oxidation and reduction processes, as was revealed by CV and DPV measurements. The particular choice of aryl substituent significantly impacts the thermal properties and electroluminescence ability of the investigated 2,6-di(thiazol-2-yl)pyridines. Image 1 • The dtpy substituted by aryl groups have been synthesized and characterized as D-A. • The aryl substituents give lowering of Eg and induce red-shift of electronic bands. • The torsional hindrance affects the ICT formation. • The aryl groups significantly impact the thermal properties and EL ability. [ABSTRACT FROM AUTHOR]

Abstract Two novel 2,4-difluorenylquinoline derivatives with different length of alkyl chain at fluorene unit (Q-F1 with methyl and Q-F2 with octyl chain) of donor-acceptor (D-A) type were synthesized and comprehensively characterized. The compounds exhibited bright emission in the blue spectral region at 400 nm and high fluorescence efficiency of 63–97% in solution. The EL measurements of OLEDs with Q-F1 , and for comparison 2,4-dicarbazolylquinoline (Q-C1) were performed to determine any correlations between the device performance and the different D units at quinoline core. These fluorenyl and carbazolyl substituted quinolines (Q-F1 and Q-C1) were found to display good thermal stability with a decomposition temperature of 301 and 416 °C, respectively. A molecule with carbazole units (Q-C1) dispersed in a host matrix exhibited higher PL quantum yield (15%) compared to Q-F1 (11%). The devices with structure ITO/PDOT:PSS/PVK:PBD:compound/Al with 15 (Q-F1) and 2 (Q-C1) wt. % of compound content in a blend were constructed. The diode based on Q-C1 emitted green light with EL maximum at 550 nm under an applied external voltage. Furthermore, by incorporation of a layer of plasmonically active silver nanowires into the device based on Q-C1 (ITO/PEDOT:PSS + AgNWs/PVK:PBD: Q-C1 (2 wt%)/Al) the noticeably more intense EL signal was detected. These results show that these compounds are promising candidates and may be used in organic light emitting devices. Graphical abstract Image 1 Highlights • Fluorene-quinolines with the diverse alkyl chain length at fluorene were prepared. • Photophysical properties of the novel compounds were examined and compared to DFT. • The length of alkyl chain promotes various photophysical properties of compounds. • Correlation between OLED performance and various donor units on the Q core was shown. • Improvement of EL signal by plasmonically active silver nanowires layer in OLED. [ABSTRACT FROM AUTHOR]

A series of ethynylated N -octylphenothiazine aldehydes (PTZ1–PTZ4) with terminal substituents of different electronic ability (p -methoxyphenyl, p -fluorophenyl, p -trifluoromethylphenyl and 2,5-bis(trifluoromethyl)phenyl) acting as A/D-π-D-A system were synthesized and fully characterized. The influence of these terminal groups on their photophysical, thermal, and biological properties was thoroughly examined and confronted with theoretical calculations. The novel compounds exhibit high thermal stability up to 238–318 °C. Compounds showed an intramolecular charge transfer (ICT) absorption band at about 399 nm and emission band at 535 nm with quantum yields between 40 and 63% in chloroform solution. All compounds exhibit positive solvatochromism in the full range of solvent polarities from hexane to DMSO, whereas in the methanol solution they demonstrate the hypsochromic shift of emission maximum compared to DMSO with significant fluorescence quenching. PTZ1–PTZ4 compounds possess a significant emission from blue to yellow region 488–542 nm, high quantum yields 24–91%, and lifetimes ranging from 6.03 to 8.56 ns in solvents of different polarity. The marked positive solvatochromism indicates the considerable ICT in PTZ1 – PTZ4 compounds. A noticeable increase in dipole moment in the excited state calculated in various solvent causes o significant red shift in the emission spectrum of PTZ1 – PTZ4. This work demonstrates the strong variation of photophysical properties with a simple alteration of the chemical structure of the phenothiazine framework by terminal groups. The toxicity of the compounds that were obtained was evaluated on cancer as well as normal fibroblast cell lines. The applicatory potential of those phenothiazines as cellular probes have been also evaluated. Unlabelled Image • Four novel phenothiazine (PTZ) derivatives with substituents of various nature were synthesized. • Photophysical properties of the compounds were thoroughly studied and compared with DTF calculations. • The solvatochromic effect of PTZs was deeply discussed and confronted with DFT. • The influence of substituents in PTZs on the dipole moment was discussed in detailed. [ABSTRACT FROM AUTHOR]

Abstract Donor-acceptor (D-A) system based on 2,4-dicarbazolyl-substituted quinolines (Q2-Q5) with different length of alkyl chain at carbazole, viz CH 3 (Q3), C 8 H 17 (Q4), C 10 H 21 (Q5), and different attachment of carbazole to quinoline core, and in addition a 4-bromo-(9 H -carbaz-2-yl)-quinoline (Q1) was designed and synthesized via Suzuki-Miyaura cross-coupling reaction to examine the influence of alkyl chain length on their photophysical behavior. The study shows a strong dependence of optical and electrochemical properties on the number of carbazole units in the molecule as well as the position of substitution of carbazole and mainly length of alkyl chain on carbazole units of studied quinoline derivatives. Emission (PL) spectra exhibit that the extension of alkyl chain length to C 8 H 17 enhances the fluorescence quantum yield and lifetime of compounds but the introduction of C 10 H 21 into molecule results in a significant reduction of luminescence ability. Additional PL spectra at 77 K of Q4 (-C 8 H 17) and Q5 (-C 10 H 21) reveal that intersystem crossing takes place with higher efficiency in Q5 and plays a superior role than possible intramolecular photoinduced electron transfer (PET) mechanism than in the case of Q4. The study of the geometry of the first singlet (S 1) and triplet (T 1) excited states of Q4 and Q5 demonstrate that the energy of the excited state in Q5 may be mostly spread as a result of the oscillations within the aliphatic hydrocarbons and in Q4 the intersystem crossing processes amplify the deactivation in the radiative path. The electrochemical investigation indicates that the oxidation potential is lower for molecules with carbazole substituted at 2- than 3-position, and among Q3 - Q5 decreases significantly from Q3 and Q4 reflecting greater ability to undergo electron removal whereas for Q5 is higher than for Q4. Graphical abstract Image 1 Highlights • The length of alkyl chain has a matter. • Carbazole-quinolines with diverse length of alkyl chain at carbazole were synthesized. • Photophysical properties of compounds were studied and compared with DFT calculations. [ABSTRACT FROM AUTHOR]

Two cyclometalated alkynylgold(III) complexes [AuCl(tpy)(C≡C–C 6 H 4 CH 3 )] ( 1 ) and [AuCl(ppy)(C≡C–C 6 H 4 CH 3 )] ( 2 ), where ppy = 2-phenylpyridine and tpy = 2-( p -tolyl)-pyridine, were successfully synthetized. Their photophysical properties were investigated by absorption and photoluminescence spectroscopy in solution, solid state, and glass matrix (77 K). Differences in solid state luminescent behaviour of the reported Au(III) complexes were correlated with packing of [AuCl(tpy)(C≡C–C 6 H 4 CH 3 )] and [AuCl(ppy)(C≡C–C 6 H 4 CH 3 )] molecules and weak interactions in the network lattices of 1 and 2 . Additionally, photoluminescence spectra of [AuCl(tpy)(C≡C–C 6 H 4 CH 3 )] in film and dispersed in solid matrix consisting of poly(9-vinylcarbazole) and (2-tert-butylphenyl-5-biphenyl-1,3,4-oxadiazole) were registered. The preliminary tests of electroluminescence ability of complex 1 were carried out. [ABSTRACT FROM AUTHOR]

Two cadmium(II) coordination compounds [Cd(NCO) 2 (tppz)] ( 1 ) and [Cd 2 (μ 1,1 -NCO) 2 (μ 1,3 -NCO) 2 (μ-tppz)] n ( 2 ) have been successfully synthesized in the reaction of CdCl 2 or Cd(NO 3 ) 2 with a versatile polydentate ligand (2,3,5,6-tetrakis(2-pyridyl)pyrazine - tppz ) and pseudohalide NCO – ions. The resulted compounds were structurally characterized by single crystal X-ray diffraction analysis and further characterized by infrared spectra, powder X-ray diffraction and thermal analysis. The photoluminescence behaviour was investigated in solid state for 1 and 2 and then compared to the free organic ligand. The luminescent properties of tppz were investigated for two polymorphs (monoclinic P2 1 / n and tetragonal I4 1 / a ). Moreover, the Hirshfeld surface analysis has been used to determine the effect of intermolecular interactions on emission properties of these polymorphs. In addition, the luminescent properties of mononuclear coordination compound were examined in acetonitrile solution. [ABSTRACT FROM AUTHOR]

Three new thiocyanate coordination compounds [Cd(NCS) 2 (μ-tppz)] n ( 1 ), [Cd(NCS)(NO 3 )(tppz)(H 2 O)] ( 2 ), [Cd 2 (μ 1,3 -NCS) 2 (NO 3 ) 2 (μ-tppz)] n ( 3 ) have been successfully synthesized in the reaction of Cd(NO 3 ) 2 ·4H 2 O or CdCl 2 ·2.5H 2 O with a versatile polydentate ligand (2,3,5,6-tetrakis(2-pyridyl)pyrazine – tppz ) and NCS − anion. The resulted compounds were structurally characterized by single crystal X-ray diffraction analysis and further characterized by infrared spectra, powder X-ray diffraction and thermal analysis. The studies demonstrated a significant impact of the reaction conditions and cadmium salt on the final molecular structures. The compounds 1 and 3 displays an infinitive one-dimensional chain made up of cadmium(II) ions linked by only through tppz bridges (in 1 ) or a single thiocyanate bridges μ 1,3 -NCS − and tppz molecules (in 3 ). The structure 2 consist of the mononuclear, heptacoordinated molecules [Cd(NCS)(NO 3 )(tppz)(H 2 O)] assembled by π⋯π and C–S⋯π type interactions into three dimensional supramolecular network. The photoluminescence behavior of 1 – 3 was investigated in solid state. In addition, the luminescent properties of the mononuclear coordination compound ( 2 ) were examined in acetonitrile solution. [ABSTRACT FROM AUTHOR]

The influence of albumin and amino acids ( l-serine, glycine, l-histidine, l-tryptophan, l-cysteine) on the properties of aluminum octacarboxyphthalocyanine hydroxide (Al(OH)PcOC) was investigated in a phosphate buffer (pH 8.0). Particular attention was paid to the spectroscopic properties and photostability of Al(OH)PcOC. The effect of albumin or amino acids on the photodegradation of Al(OH)PcOC was examined in water using red light: 685 nm and daylight irradiation. Analysis of kinetic curves indicated that interaction with those molecules increases the photostability of Al(OH)PcOC. The molecular structure of Al(OH)PcOC complexes (in vacuum and in water) with axially or equatorially coordinated amino acids was studied by the B3LYP/6-31G* method, and the effects on molecular structure and electronic absorption spectrum were investigated on the basis of the density functional theory. The calculation results revealed that axial coordination significantly reduces the non-planarity of the phthalocyanine ring, and, thus, alters the electronic structure. On the other hand, hydrogen bonding of phthalocyanine side COOH groups with amino acids, in equatorial complexes, does not change the structure within the center of the phthalocyanine, and causes only a slight increase in UV-vis bands intensity, which is in perfect agreement with experimental data. [ABSTRACT FROM AUTHOR]

The pseudotetrahedral complexes of [Cu(PPh 3 ) 2 (L)], where L=8-hydroxy-2-methylquinoline-7-carboxylic acid ( 1 ), 8-hydroxy-2,5-dimethylquinoline-7-carboxylic acid ( 2 ) or 5-chloro-8-hydroxy-2-methylquinoline-7-carboxylic acid ( 3 ) have been synthesized and structurally characterized by X-ray crystallography. Their properties have been examined through combinations of IR, NMR, electronic absorption spectroscopy and cyclic voltammetry. The complexes exhibit extraordinary photophysical properties. Complex (1) in solid state exhibits an emission quantum yield of 4.67% and an excited life time of 1.88 ms (frozen DCM solution up to 6.7 ms). When dissolved in a coordinating solvent (acetonitrile) the charge transfer emission was quenched on a microsecond scale. [ABSTRACT FROM AUTHOR]

In this work, a series of six rhenium(I) complexes bearing 2,2′:6′,2″-terpyridine (terpy), 2,6-di(thiazol-2-yl)pyridine (dtpy), and 2,6-di(pyrazin-2-yl)pyridine (dppy) with appended quinolin-2-yl and N-ethylcarbazol-3-yl groups were prepared and spectroscopically investigated to evaluate the photophysical consequences of both the trisheterocyclic core (terpy, dtpy and dppy) and the heterocyclic substituent. The [ReCl(CO) 3 (Ln-κ2N)] complexes are regarded as ideal candidates for getting structure–property relationships, while terpy -like framework represents an excellent structural backbone for structural modifications. The replacement of the peripheral pyridine rings of 2,2′:6′,2″-terpyridine by thiazoles and pyrazines resulted in a significant red-shift of the absorption and emission of [ReCl(CO) 3 (Ln-κ2N)] due to stabilization of the ligand-centred LUMO orbital. Both quinoline and N-ethylcarbazole are extended π-conjugation organic chromophores, but they differ in electron-donating abilities. The low-energy absorption band of Re(I) complexes with the triimine ligands bearing quinolin-2-yl group was contributed by the metal-to-ligand charge-transfer (MLCT) electronic transitions. The introduction of electron-donating N-ethylcarbazol-3-yl substituent into the triimine acceptor core resulted in the change of the character of the HOMO of Re(I) complexes and a significant increase of molar absorption coefficients of the long-wavelength absorption, which was assigned to a combination of 1MLCT and 1ILCT (intraligand charge-transfer) transitions. Regardless of the appended heteroaromatic group, the emitting excited state of Re(I) terpy -based complexes was demonstrated to have predominant 3MLCT character, as evidenced by comprehensive studies including static and time-resolved emission spectroscopy along with ultrafast transient absorption measurements. The diodes with Re(I) complexes dispersed molecularly in a PVK:PBD matrix were emissive and effects of the complex structure on colour of emitted light and its intensity was pronounced. • A series of Re(I) complexes with terpy-like ligands was prepared. • Impact of the ligand architecture on the photophysical properties was investigated. • The character of the emitting excited state was determined. • The capacity of obtained compounds for electroluminescence was primarily tested. [ABSTRACT FROM AUTHOR]

Four new 1-phenyl-1H-phenanthro[9,10-d]imidazole derivatives containing N-donor substituents at the C2 position were synthesized using simple condensation reaction. Thermal, electrochemical, spectroelectrochemical, and optical properties of synthesized compounds were investigated, while their purity was confirmed by NMR spectroscopy and HRMS. They are characterized by high thermal stability above 243 °C. Electrochemical measurements were carried out in dichloromethane (DCM) and THF. Quasi-reversible peaks of N2 and N5 oxidation as opposed to irreversible oxidation in THF were observed in DCM. N2 – N5 exhibit at least three well-developed absorption bands, which is typical for π→π* transitions. All phenanthro[9,10-d]imidazole derivatives exhibit high photoluminescence quantum yields in the range of 34%–82% in solution. Additionally, the electroluminescent ability of the synthesized compounds was preliminarily tested. [Display omitted] • Novel phenanthro[9,10-d]imidazole derivatives were synthesized in good yield. • To better understand the condensation reactions, a four-step reaction mechanism has been proposed. • The detailed theoretical calculation was performed for electrochemical and photophysical studies. • The electroluminescent ability of the synthesized compounds was preliminarily tested. [ABSTRACT FROM AUTHOR]

2,6-Bis(thiazol-2-yl)pyridines functionalized with 9-anthryl (L1), 9-phenanthryl (L2), and 1-pyrenyl (L3) groups were used for the preparation of [Pt(Ln)Cl]CF3SO3 (1–3). The constitution of the Pt(II) complexes was determined by 1H and 13C NMR spectroscopy, HR-MS spectrometry, elemental analysis and X-ray analysis (for (1)). The electrochemical and photophysical properties of [Pt(Ln)Cl]CF3SO3 were compared with the behaviour of the Pt(II) complexes with aryl-substituted 2,2′:6′,2′′-terpyridine ligands. What is noteworthy is that the coordination ability of dtpy toward the Pt(II) centre was investigated for the first time. All complexes were tested in vitro by MTS assay on four tumor cell lines, A2780 (ovarian carcinoma), HTC116 (colon rectal carcinoma), MCF7 (breast adenocarcinoma), and PC3 (prostate carcinoma) and on normal primary fibroblasts. Compounds (1–3) showed a dose dependent antiproliferative effect in the A2780 cell line with (3) > (2) > (1) and this loss of A2780 cell viability was due to a combination of an apoptotic cell death mechanism via mitochondria and autophagic cell death. Exposure to IC50 concentration of (2) induced an increase in the number of apoptotic nuclei and a depolarization of the mitochondrial membrane which is consistent with the induction of apoptosis while exposure to IC50 concentration of (3) showed an increase in the apoptotic nuclei with a slight hyperpolarization of the mitochondrial membrane that might indicate an initial step of apoptosis induction. The complexes (2) and (3) induce an increase in the production of intracellular ROS which is associated with the trigger of the apoptotic pathways. The ROS production was augmented by the presence of oxidants and correlated with an increase of oxygen radicals. The IC50 of (2) and (3) (4.4 μM and 2.9 μM, respectively) was similar to the IC50 of cisplatin (3.4 μM) in the A2780 cell line, which together with their low cytotoxicity in normal fibroblasts, demonstrates their potential for further studies. [ABSTRACT FROM AUTHOR]

Five novel derivatives of pyrene, substituted at positions 1,3,6,8 with 4-(2,2-dimethylpropyloxy)pyridine ( P1), 4-decyloxypyridine ( P2), 4-pentylpyridine ( P3), 1-decyl-1,2,3-triazole ( P4), and 1-benzyl-1,2,3-triazole ( P5), are obtained through a Suzuki-Miyaura cross-coupling reaction or CuI-catalyzed 1,3-dipolar cycloaddition reaction, respectively, and characterized thoroughly. TGA measurements reveal the high thermal stability of the compounds. Pyrene derivatives P1- P5 all show photoluminescence (PL) quantum yields (Φ) of approximately 75 % in solution. Solid-state photo- and electroluminescence characteristics of selected compounds as organic light-emitting diodes are tested. In the guest-host configuration, two matrixes, that is, poly( N-vinylcarbazole) (PVK) and a binary matrix consisting of PVK and 2-tert-butylphenyl-5-biphenyl-1,3,4-oxadiazole (PBD) (50:50 wt %), are applied. The diodes show red, green, or blue electroluminescence, depending on both the compound chemical structure and the actual device architecture. In addition, theoretical studies (DFT and TD-DFT) provide a deeper understanding of the experimental results. [ABSTRACT FROM AUTHOR]

New rhenium(I) tricarbonyl complexes based on the phenanthroline ligand were designed and synthesized to investigate the role of carbazole (cbz) and pyrrolidine (pyrr) substituents in determining thermal, electrochemical and optoelectronic properties. Both pyrr and cbz are electron-releasing substituents, but they differ in the steric hindrance and electron delocalization ability. The impact of pyrr and cbz on ground- and excited-state properties of [ReCl(CO) 3 (cbz 2 -CH 3 phen)] (1) and [ReCl(CO) 3 (pyrr 2 -CH 3 phen)] (2) were investigated with a range of techniques including cyclic voltammetry, absorbance and emission spectroscopies, transient absorption spectroscopy, and they were discussed in comparison with the model chromophore [ReCl(CO) 3 (CH 3 phen)] (3). Experimental results were supported by theoretical calculations. The most striking difference between the pyrr and cbz groups was seen in their impact on the LUMO energy level. While the attached carbazole groups decreased the LUMO energy of 1 , the pyrrolidine ones in 2 resulted in the rise of LUMO energy level compared to the model chromophore. For both 1 and 2 , the HOMO got energetically destabilized in agreement with electro-donor abilities of pyrr and cbz substituents. Structural modification of phen backbone resulted also in changes of distribution of occupied MOs of 1 and 2 in relation to 3. Experimentally, it was manifested in noticeable changes of electrochemical and photophysical behaviour of the resulting Re(I) complexes in relation to the model chromophore. [Display omitted] • A series of Re(I) complexes with phen-like ligands was prepared. • The character of the ground and excited state of compounds was determined. • The effect of donor groups was explored experimentally and theoretically. [ABSTRACT FROM AUTHOR]

In this study, the synthesis and physicochemical properties (thermal, electrochemical and optical) of three phenanthro[9,10-d]imidazole derivatives with N-donor substituents (PI-1 - PI-3) was presented. All compounds were obtained by condensation reactions with a yield in the range of 61–70%. Their structure was confirmed by NMR spectroscopic methods (1H, 13C, H–H COSY, H–C HMQC and H–C HMBC). The synthesized derivatives were characterized by high thermal stability (above 300 °C). Two of them (PI-1 and PI-3) showed a fully reversible oxidation process, which allowed detailed spectroelectrochemical and electrochemical studies. Absorption and emission properties were tested in four solvents of different polarity. These compounds showed high quantum yields in the range from 18 to 80%. Studies on physicochemical properties have been extended to include detailed theoretical considerations. Image 1 • A series of phenanthro[9,10-d]imidazole derivatives with N-donor substituents were investigated. • All derivatives were showed high thermal stability. • These compounds were characterized by high quantum yields in the range from 18 to 80%. • Detailed theoretical calculation were performed for electrochemical and photophysical studies. [ABSTRACT FROM AUTHOR]

Two platinum(II) coordination compounds, [PtCl(4′-R1-terpy)](SO 3 CF 3) (1) and [PtCl(4′-R2-terpy)](SO 3 CF 3) (2), with 4′-(2-pyridyl)-2,2′:6′,2″-terpyridine (4′-R1-terpy) or 4′-(3-pyridyl)-2,2′:6′,2″-terpyridine (4′-R2-terpy) were synthesized and the impact of the pendant pyridyl ring on the structure and cytotoxic activity of Pt(II)-terpyridine complexes was explored. The single-crystal X-ray diffraction analysis confirmed square planar coordination of the cations [PtCl(4′-Rn-terpy)]+. The mode of binding of 1 and 2 to calf thymus DNA was examined by UV–Vis absorption titration, ethidium displacement assay and reaction with 9-ethylguanine, and the mixed covalent-intercalative mode was demonstrated. The cytotoxicity of the Pt(II) complexes against six cancer cell lines and three normal ones was determined using MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) assay and compared to cisplatin. The IC 50 values for the compound 2 towards the cancer cell lines are in the low micromolar range. Most remarkably, 2 was over 4 times more effective than 1 and cisplatin against non-small lung adenocarcinoma (A549), and its selectivity index was ~60–80 times higher than that for 1 and cisplatin. The mechanisms underlying the loss of viability under treatment of 2 was further investigated including F-actin staining, mitotic index analysis, cytometric cell cycle analysis, Fluorescein isothiocyanate (FITC) -conjugated Annexin V antibody and propidium iodide (PI) staining, measurements of reactive oxygen species (ROS) in cells, analysis of changes in the mitochondrial mass and potential and quantitative real time polymerase chain reaction (qRT-PCR) genes analysis. The compound 2 was found to have a pro-oxidative effect by strong stimulation of cells for the production of reactive oxygen species and cytostatic effect through cell cycle arrest. 4′-(2-pyridyl)-2,2′:6′,2″-terpyridine and 4′-(3-pyridyl)-2,2′:6′,2″-terpyridine were used to synthetize platinum(II) coordination compounds, and the impact of the pendant pyridyl ring on the structure and cytotoxic activity of Pt(II)-terpyridine complexes has been investigated. The compounds were found to be cytotoxic, displaying mixed covalent-intercalative mode of interaction with calf thymus DNA. Unlabelled Image • The cytotoxicity of two planar platinum(II) complexes was investigated. • The impact of the pendant pyridyl ring attached to the terpyridine ligand was evidenced. • The mixed covalent-intercalative mode of interaction with calf thymus DNA was shown. • High selectivity index for Pt(II) complex of terpyridine substituted with 3-pyridyl. • Promising alternative to cisplatin [ABSTRACT FROM AUTHOR]