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This paper describes the synthesis and characterization of new organic semiconductors based on pyrrolo[1,2-i][1,7]phenanthrolines in the form of thin layers. The thin layers, produced via the spin coating method (with a thickness of 10–11 μm), were investigated for their electrical and optical properties. After heat treatment at temperatures ranging from 210 to 240 °C, the layers displayed consistent and reproducible properties. The layers exhibited n-type semiconductor behavior, with a thermal activation energy (Ea) in the range of 0.75–0.78 eV. Additionally, the layers showed transmittance values of 84–92% in the visible and near-infrared spectral ranges, with a direct optical band gap (Egod) ranging from 3.13 to 4.11 eV. These thin layers have potential applications in electronic devices such as thermistors, as well as in nanoelectronics and optoelectronics. Overall, these new organic semiconductors show promising properties for practical implementation in various electronic applications.

This study presents the synthesis, structural characterization, and in vitro evaluation of anticancer activity of some newly benzo[f]quinoline derivatives. The synthesis is facile and efficient, involving two steps: quaternization of nitrogen heterocycle followed by a [3+2] dipolar cycloaddition reaction. The synthesized compounds were characterized by FTIR, NMR, and X-ray diffraction on monocrystal in the case of compounds 6c and 7c. An in vitro single-dose anticancer assay of eighteen benzo[f]quinoline compounds, quaternary salts, and cycloadducts, was performed. The results showed that the most active compounds were quaternary salts 3d and 3f with aromatic R substituents. Quaternary salt 3d revealed non-selective activity against all types of cancer cells, while salt 3f exhibited a highly selective activity against leukemia cells. Compound 3d also presented remarkable cytotoxic efficiency against four distinct types of cancer cells—namely, non-small cell lung cancer HOP–92, melanoma LOX IMVI, melanoma SK–MEL–5, and breast cancer MDA–MB–468. Compound 3f was selected for five-dose screening. The study also includes SAR correlations.

A potential microtubule destabilising series of new indolizine derivatives was synthesised and tested for their anticancer activity against a panel of 60 human cancer cell lines. Compounds 11a, 11b, 15a, and 15j showed a broad spectrum of growth inhibitory activity against cancer cell lines representing leukaemia, melanoma and cancer of lung, colon, central nervous system, ovary, kidney, breast, and prostate. Among them, compound 11a was distinguishable by its excellent cytostatic activity, showing GI50 values in the range of 10–100 nM on 43 cell lines. The less potent compounds 15a and 15j in terms of GI50 values showed a high cytotoxic effect against tested colon cancer, CNS cancer, renal cancer and melanoma cell lines and only on few cell lines from other types of cancer. In vitro assaying revealed tubulin polymerisation inhibition by all active compounds. Molecular docking showed good complementarity of active compounds with the colchicine binding site of tubulin., Graphical Abstract

This work reports a study on structural, electrical and optical properties of some recently synthesized pyrrolo[1,2

This work emphasizes the synthesis strategies and antiproliferative related properties of fused pyrrolo-pyridine (including indolizine and azaindoles) and pyrrolo-(iso)quinoline derivatives recently reported in literature.

Several new cyano-substituted derivatives with pyrrolo[1,2-a]quinoline and pyrrolo[2,1-a]isoquinoline scaffolds were synthesized by the [3 + 2] cycloaddition of (iso)quinolinium ylides to fumaronitrile. The cycloimmonium ylides reacted in situ as 1,3-dipoles with fumaronitrile to selectively form distinct final compounds, depending on the structure of the (iso)quinolinium salt. Eleven compounds were evaluated for their anticancer activity against a panel of 60 human cancer cell lines. The most potent compound 9a showed a broad spectrum of antiproliferative activity against cancer cell lines representing leukemia, melanoma and cancer of lung, colon, central nervous system, ovary, kidney, breast and prostate cancer. In vitro assays and molecular docking revealed tubulin interaction properties of compound 9a.

Microwave (MW) assisted reactions have became a powerful tool in azaheterocycles chemistry during the last decades. Five and six membered ring azaheterocycles are privileged scaffolds in modern medicinal chemistry possessing a large variety of biological activity. This review is focused on the recent relevant advances in the MW assisted reactions applied to azaheterocyclic derivatives and their medicinal chemistry applications from the last five years. The review is divided according to the main series of azaheterocycles, more precisely 5- and 6-membered ring azaheterocycles (with one, two, and more heteroatoms) and their fused analogues. In each case, the reaction pathways, the advantages of using MW, and considerations concerning biological activity of the obtained products were briefly presented.

Three series of fused pyrrolophenanthroline derivatives were designed as analogues of phenstatin and synthesized in two steps starting with 1,7-phenanthroline, 4,7-phenanthroline and 1,10-phenanthroline, respectively. Two (Compounds 8a and 11c) of the four compounds tested against a panel of sixty human cancer cell lines of the National Cancer Institute (NCI) exhibited significant growth inhibition activity on several cell lines. Compound 11c showed a broad spectrum in terms of antiproliferative efficacy with GI50 values in the range of 0.296 to 250 &mu, M. Molecular docking studies indicated that Compounds 8a and 11c are accommodated in the colchicine binding site of tubulin in two different ways.

Some indolizines with phenanthroline skeleton derivatives have been investigated using steady state absorption, emission and time resolved fluorescence techniques. The effects of the substituents on the electronic absorption spectra and fluorescence emission have been demonstrated. The fluorescence decay curves exhibit one or two decay times. The emission lifetime measurements revealed values of 3–5 ns under the excitation with 370 nm. The quantum yield was also determined. The quenching process of emission using picric acid as quencher was characterized by Stern-Volmer plots. The phenanthroline derivatives 2 and 5 possess high efficiency for the detection of picric acid.

A comparative study regarding cycloaddition versus amidation reactions of 2-amino-2-oxoethyl-phenanthrolinium ylides to activated alkynes and alkenes is presented. The reaction pathway is different, depending on dipolarophile (with triple or double bond) and ylide structures. The monoenamidation reaction proved to be stereoselective leading to a Z-stereochemistry on the acrylate double bond. The structures of all newly synthesized compounds have been proved by spectral analysis (NMR and IR) and in some cases by X-ray diffraction.

Fifteen new 1,10-phenanthrolines disubstituted at positions 2 and 9 via amide bonds with different heterocycles have been designed and synthesized as G-quadruplex DNA stabilizers. Ten compounds were evaluated for the in vitro anticancer activity against 60 human tumor cell lines panel, four of them showing a very good inhibitory activity on several cell lines. To assess the ability of the most active compounds to interact with G-quadruplex DNA (G4-DNA), circular dichroism experiments were performed. The potency of the compounds to stabilize the G4-DNA has been shown from the thermal denaturation experiments. The mechanism of compounds binding to DNA and to G4-DNA was theoretically investigated by molecular docking studies. The experimental results demonstrated excellent capacity of the two compounds bearing two pyridin-3-yl residues (methylated and non-methylated) to act as selective G-quadruplex binders with promising anticancer activity.

New fluorescent anthracene-based indolizine derivative has been synthesized by appendix of the anthracene moiety via “click” chemistry at the first position of indolizinic core. The new product has been carefully characterized and its absorption-emission properties studied in aqueous buffer solutions at different pH values and also compared to its precursor containing only pyridyl-indolizinic core. The anthracenemodified indolizine and its precursor were tested for DNA binding using agarose gel electrophoresis, UV–vis and fluorescence experiments. The comparative experimental data were in accordance to the molecular docking simulation of the corresponding systems using the Yassara computer program. Both experimental and simulation results suggest that the anthracene-modified indolizine has a superior affinity for the DNA than its precursor due to much lower values of binding energy and dissociation constant of the corresponding complex.

Temperature dependence of d. c. electric conductivity of some recently synthesized heterocyclic compounds, 4,4′-bipyridine and indolizine derivatives, in thin films (d = 0.27–0.51 μm) spin-coated from chloroform solutions onto glass, is studied. The investigated compounds are polycrystalline (as shown by X-ray Diffraction analysis) and show typical n-type semiconductor behavior. The activation energy of d. c. electric conduction ranges between 1.55 and 2.33 eV. Some correlations between semiconducting characteristics and essential features of molecular structure of organic compounds have been established. In the higher temperature range (400–520 K), the electronic transport properties in present compounds can be explained in the frame of band gap representation model, while in the lower temperature range (300–350 K), the Mott's variable-range hopping conduction model can be conveniently used.

Aromatic cycloimmonium salts underwent different reaction pathways when treated with ethyl cyanoformate in triethyl amine medium, including selective γ-cyano substitutions (in case of phenanthrolinium and quinolinium salts) and 3+2 dipolar cycloadditions (for phthalazinium and isoquinolinium salts). When using phthalazinium salts, besides the 3+2 cycloaddition products (imidazo[2,1-a]phthalazines), we obtained 8,8a,16,16a-tetrahydropyrazino-[2,1-a;4,5-a′]-diphthalazines as secondary products via a 3+3 cycloaddition dimerization. The structures of the synthesized compounds have been proved by spectral data, and X-ray diffraction for three of the new derivatives.

We have designed and synthesized a series of novel, supramolecular, long-lived fluorescent probes based on the host-guest inclusion complexes formation between fluorescent indolizinyl-pyridinium salts and &beta, cyclodextrin. Fluorescence and electrospray ionisation mass spectrometry experiments, supported by theoretical molecular docking studies, were utilized in the monitoring of the inclusion complexes formation, evidencing the appearance of corresponding 1:1 and 1:2 species. Additionally, the influence of the guest molecule over the aggregation processes of the cyclodextrin inclusion complexes was investigated by transmission electron microscopy. The absence of cytotoxicity, cellular permeability, long-lived intracellular fluorescence, and in time specific accumulation within acidic organelles identified the investigated supramolecular entities as remarkable candidates for intracellular fluorescence probes. Co-staining experiments using specific organelle markers revealed the fact that, after a 24-h incubation period, the inclusion complexes accumulate predominantly in lysosomes rather than in mitochondria. This study opens new possibilities for a broad range of fluorescent dyes with solubility and high toxicity issues, able to form inclusion complexes with &beta, cyclodextrin, to be tested as intracellular fluorescence probes.

Six new fused isoquinoline based compounds (compounds 5a–c with pyrrolo[2,1-a] isoquinoline structure and compounds 6a–c with imidazo[2,1-a]isoquinoline skeleton) have been synthesized using the [3 + 2] cycloaddition of the several in situ generated cycloimmonium ylides to ethyl propiolate or ethyl cyanoformate. All the synthesized compounds have been investigated in solution by UV–VIS absorption, steady and time-resolved fluorescence methods. The effect of the substituents on the spectral characteristics has been demonstrated. These derivatives displayed an intense emission between 360 and 420 nm. The emission quantum yields (Φ = 0.54–0.64) of pyrroloisoquinoline derivatives in dimethylsulfoxide (DMSO) were significantly higher than those of imidazoquinolines (0.03–0.16). The fluorescence decay of isoquinoline derivatives follows a biexponential law. A noticeable response of these isoquinoline derivatives to sodium hydroxide was observed.

The synthesis and structure of the new organic proligand 2-formylpyridine S-methyl-isothiosemicarbazone in a bi-protonated form (HL.2HCl) and its coordination compounds with Mn(II) - [Mn(HL)·Cl2], Co(III) - [CoL2]·ClO4, Ni(II) - [Ni(HL)2]·2ClO4, Cu(II) - [Cu(HL)Cl2]·(H2O), Zn(II) - [Zn(HL)2]·2(ClO4)·(H2O) and Pd(II) - [Pd(HL)·Cl]·Cl are reported. According to the X-ray investigation, the ligand has the molecular form of HL in the case of Mn(II), Cu(II), Zn(II) and Pd(II) compounds, and the deprotonated form L− in case of the Co(III) complex. The ligand coordinates to the metal ions via a N,N,N set of donors atoms in case of Zn(II), Cu(II) and Co(III). For Mn(II), the ligand coordinates via N,N donor atoms, whereas in the case of Pd(II) metal ions, the coordination sphere is N,N,S. This latter coordination mode (via S(CH3)) has been previously reported in case of salicylaldehyde S-alkyl-isothiosemicarbazones.

Electric (d.c. conduction mechanism, the influence of environmental humidity, thermistor effect) and optical properties of new five substituted calixarene derivatives in thin films have been studied. The films behave as typical n-type polycrystalline semiconductors with activation energy of the electric conduction between 0.26 and 2.36 eV. In the higher temperature range, the electron transport was explained in the frame of the band gap representation model, while at lower temperatures, the Mott’s variable-range hopping conduction model was found as appropriate. In terms of electric conductivity, these compounds are practically insensitive to ambient humidity below 53% RH, their sensitivity increasing greatly with the humidity in the range of 53–98% RH. Study of optical absorption spectra in the photon energy range of 0.71–4.03 eV (UV–Vis–NIR) revealed direct optical band gaps between 2.64 and 3.83 eV. Actual compounds show promising potential for thermistor applications.

Several new conjugates of tert-butylcalix[4]arenes bearing different 1-substituted triazoles at the lower rim were synthesized via click chemistry. The products were tested towards complexation of metal ions exhibiting pronounced selectivity towards Hg2+. The 1H NMR titration results for ligand 12a show formation of L:Hg2+ complexes with various stoichiometries, logβ(1:1)=6.8, logβ(2:1)=11.9, logβ(2:2)=15.1 in CDCl3:CD3CN 1:1.

The preparation and characterization of a supramolecular host–guest inclusion complex between a fluorescent indolizinyl-pyridinium salt and β-cyclodextrin is reported. The formation of the inclusion complex was investigated by ESI-MS experiments, transmission electron microscopy, Job's plot investigations and molecular docking studies, proving the formation of 1 : 1 and 1 : 2 species. Several interesting features of the investigated fluorescent indolizinyl-pyridinium salt/β-cyclodextrin inclusion complexes like the absence of cytotoxicity, cellular permeability, long-lived intracellular fluorescence and selective accumulation within acidic organelles made them remarkable candidates for the intracellular labelling of acidic organelles (lysosomes or mitochondria). Taking into account that a number of reported or commercially available cell staining dyes with low toxicity and solubility have already been used in cyclodextrin formulations with good results regarding the improvement of their properties, our results showed that this approach may also work with new and interesting toxic dyes capable of forming host–guest inclusion complexes with cyclodextrins.

Three classes of fused bipyridine heterocycles were designed, synthesized and evaluated for their antimycobacterial activities. The method for preparation of fused bipyridine derivatives is straight and efficient. The primary antimycobacterial screening reveals that mono-indolizine mono-salts are displaying potency superior to the second-line antitubercular drugs Cycloserine and Pyrimethamine and, equal as the first line anti-TB Ethambutol. The data from Cycle-2 screening assay (MIC, MBC, LORA, intracellular (macrophage) drug screening, and MTT cell proliferation) confirm the promising anti-TB results from Cycle-1 for mono-indolizine mono-salts. These data indicate that mono-indolizine mono-salt 6d is a potent compound against both replicating and non-replicating Mycobacterium tuberculosis, is active against both extracellular and intracellular organisms, has a bacteriostatic mechanism of action and has basically no toxicity. We see no influence concerning the anti-TB activity of the fused-pyridine substituents.

Palladium(II) complexes with Schiff bases ligands derived from salicylaldehyde and amino acids (Ala, Gly, Met, Ser, Val) have been synthesized and characterized by Fourier transform (FT)-IR, UV-Vis and (1)H-NMR spectroscopy. The electrospray mass spectrometry (ES-MS) spectrometry confirms the formation of palladium(II) complexes in 1/2 (M/L) molar ratio. All the Pd(II) complexes 1, [Pd(SalAla)2]Cl2; 2, [Pd(SalGly)2]Cl2; 3, [Pd(SalMet)2]Cl2; 4, [Pd(SalSer)2]Cl2; 5, [Pd(SalVal)2]Cl2; have shown antibacterial activity against Gram-positive bacteria Staphylococcus aureus and Gram-negative bacteria Escherichia coli.

A series of UDP-D-glucose derivatives and precursors that have been modified at C-3 were synthesised from D-glucose as potential chain terminators of beta-glucan biosynthesis. None of the UDP-derivatives or the precursors tested displayed significant anti-fungal activity in a series of germination assays on the dermatophyte Trichophyton rubrum.

Temperature dependences of electric conductivity and thermoelectric power of some recently synthesized organic compounds, 4-tert-butylcalix[4]arene derivatives, are studied. Thin-film samples (d = 0.10–0.40 μm) spin-coated from chloroform solutions onto glass substrates were used. Organic films with reproducible electron transport properties can be obtained if, after deposition, they are submitted to a heat treatment within temperature range of 295–575 K. The studied polycrystalline compounds show typical p-type semiconductor behavior. The activation energy of the electric conduction ranges between 0.82 and 1.12 eV, while the ratio of charge carrier mobilities was found in the range of 0.83–0.94. Some correlations between semiconducting parameters and molecular structure of the organic compounds have been discussed. In the higher temperature ranges (T > 420 K), the electron transport in examined compounds can be interpreted in terms of the band gap representation model, while in the lower temperature range, the Mott's variable-range hopping conduction model was found to be appropriate. The investigated compounds hold promise for thermistor applications.

Temperature-dependent d.c. electric conductivity of some recently synthesized indolizine derivatives is studied. Thin-film samples (d = 0.10–0.30 μm) spin-coated from chloroform solutions onto glass substrates were used. Organic films with reproducible electric properties can be obtained by submitting as-prepared samples to a heat treatment within temperature range of 301–493 K. The studied polycrystalline compounds show typical n-type semiconductor behavior. The activation energy of the electric conduction ranges between 0.32 and 1.07 eV. Some correlations between semiconducting characteristics and molecular structure of the organic compounds have been discussed. In the higher temperature range (T > 415 K), the electron transport in present compounds can be interpreted in terms of the band gap representation model, while in the lower temperature range (T < 339 K), the Mott’s variable-range hopping conduction model was found to be suitable.

A simple route to introduce various heterocycles, derivatives of dipyridyls and indolizines on the lower rim of the para-tert-butylcalix[4]arene via ester bond formation to afford 1,3-disubstituted conjugates is described. The conformation of the new compounds and some intermolecular interactions are discussed on the basis of X-ray and NMR analyses. Preliminary complexation properties of some of the new tert-butylcalix[4]arene heterocyclic conjugates with Cu (II), Co (II) and Ni (II) were studied by means of UV–Vis titration.

The electrical conductivity (σ) and thermoelectric power (S) of six newly synthesized high resistivity organic salts, N-(p-R-phenacyl)-1,7-phenanthrolinium bromides (T compounds), were investigated as a function of temperature. Thin-film samples (d = 0.11–2.22 μm) deposited from ethanol solutions (an immersion technique) onto glass substrates were used. It was established that samples with stable structure and reproducible electronic transport properties can be obtained if, after their deposition, respective films are submitted to a heat treatment within temperature range 297–513 K. The surface morphology of organic samples was examined by AFM technique, corroborated to optical microscopy. The studied organic salts behave as typical n-type polycrystalline semiconductors. The thermal activation energy of electrical conduction laid in the range 0.78–0.92 eV, while the ratio of charge carrier mobilities ranged between 1.09 and 1.24. The correlations between semiconducting parameters (activation energy of electrical conduction, ratio of carrier mobilities, etc.) and molecular structure of the compounds have been discussed. In the higher temperature range (390–513 K), the model based on band gap representation is suitable for the explanation of electronic transfer in investigated compounds, while in the lower temperature range, the Mott's variable-range hopping conduction model was found to be appropriate. The present compounds are also promising for thermistor applications.

In this work, temperature dependences of electrical conductivity and thermoelectric power, for some recently synthesized nonsymmetrical bisindolizines, are studied. Thin-film samples (d = 0.10–0.30 μm) spin-coated from dichloromethane solutions onto glass substrates were used. Organic films with reproducible electronic transport properties can be obtained if, after deposition, they are subjected to a heat treatment within the temperature range of 301–541 K. The studied organic compounds show typical p-type semiconductor behavior. The activation energy of electrical conduction was found in the range 1.00–1.26 eV, while the ratio of charge carrier mobilities ranged between 0.90 and 0.97. The correlations between determined semiconducting parameters and specific features of molecular structure of the compounds have been discussed. In the higher temperature range (363–541 K), the electronic transport in actual compounds can be interpreted by using the band gap representation model, while for lower temperatures, Mott's variable-range hopping conduction model was found to be appropriate.

Temperature-dependent electrical conductivity and thermoelectric power of some recently synthesized fused heterocyclic compounds (nonsymmetrical bisindolizines), are studied. Thin-film samples ( d = 0.10–0.20 μm) deposited from dichloromethane solutions onto glass substrates were used. Organic films with reproducible electronic transport properties can be obtained if, after deposition, they are submitted to a heat treatment within temperature range 300–600 K. The studied compounds show typical p-type semiconductor behavior. The activation energy of the electrical conduction ranges between 0.90 and 1.17 eV, while the ratio of charge carrier mobilities was found in the range 0.94–0.97. Some correlations between semiconducting parameters and molecular structure of the organic compounds have been discussed. In the higher temperature range (373–601 K), the electronic transport in examined compounds can be interpreted in terms of the band gap representation model, while in the lower temperature range, the Mott's variable-range hopping conduction model was found to be appropriate.

The temperature dependences of electrical conductivity, σ , and Seebeck coefficient, S , for some new pyridium monoquaternary salts derivatives, 1-( p -R-phenacyl)-4-{[(1′-ethylcarboxylate)-(3′- p -R′-phenacyl)]-7′-indolizinyl}pyridinium bromides have been studied. The film samples ( d = 0.08–0.28 μm) have been deposited onto glass by an immersion technique (dimethylformamide was used as a solvent). The investigated compounds behave as typical p-type polycrystalline semiconductors. The activation energy of electrical conduction ranged between 0.65 and 1.72 eV, while the ratio of charge carrier mobilities laid in the range (0.60–0.83). The model based on band gap representation is suitable in explaining the electronic transport in present compounds in the higher temperature range (385–500 K).

Thin films of new pyrrolo [ 1 , 2 - a ] [ 1 , 10 ] phenanthroline derivatives have been investigated by ultraviolet photoelectron spectroscopy, with a view of future applications in optoelectronic devices. The electronic band structure of investigated compounds (for electron energies ⩽ 25 eV ) is to a great extent determined by substituent (R = NO 2 , Cl) induced transformations of molecular orbitals.