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A gold(I)-catalyzed 6-endo-dig cyclization of aromatic 1,5-enyne was developed to synthesize 2-(naphthalen-2-yl)aniline. The functional group tolerance of this cyclization was examined systematically and a possible mechanism was proposed. The derivatization of 2-(naphthalen-2-yl)aniline was carried out to facile access to benzo[α]carbazole, benzo[c,h]cinnoline and dibenzo[i]phenanthridine derivatives in a divergent way.

Pharmacological inactivation of antitumor drugs toward healthy cells is a critical factor in prodrug development. Typically, pharmaceutical chemists graft temporary moieties to existing antitumor drugs to reduce their pharmacological activity as much as possible. Here, we report a platform where the structure of the prodrug excludes the preexisting antitumor drug motif and is based on an inactive synthetic precursor able to generate the cytotoxic agent by bioorthogonal cyclization within a tumor environment. Using phenanthridines as cytotoxic model compounds, we designed ring-opened biaryl precursors that generated the phenanthridines through bioorthogonal irreversible imination. This reaction was triggered by reactive oxygen species, commonly overproduced in cancer cells, able to convert a vinyl boronate ester function into a ketone that subsequently reacted with a pendant aniline. An inactive precursor was shown to engender a cytotoxic phenanthridine against KB cancer cells. Moreover, the kinetic of cyclization of this prodrug was extremely rapid (˂ 10 ms) inside living cells of KB cancer spheroids so as to circumvent drug action.

The binuclear cadmium complexes in which the metal atoms are linked by two chelate-bridging carboxylate anions, [Cd2L2(µ2-(Рiv)2(κO,κO'-(Рiv)2] (L is 2,4-lutidine, phenanthridine, and 2,2'-bipyridine; and Рiv is pivalate anion), and the complexes with the “Chinese lantern” structure in which the cadmium atoms are linked by four bridging carboxylate anions, [Cd2L2(µ2-(Рiv)4] (L is 2,3-cyclododecenopyridine (Сdpy)) and [Cd2(L)2(µ2-(PfAc))4] (L is 1,10-phenanthroline, and PfAc is pentafluorophenylacetate anion), are considered. The two-bridge and four-bridge isomers of each binuclear [Cd2L2(Рiv)4] complex with the monodentate and chelating N-donor ligands are calculated by the density functional theory using four different approximations. The stabilities of the isomers are compared and conclusions about the factors leading to the formation of complexes of this or another structure are made on the basis of the calculation data.

An N-heterocyclic carbene ligand precursor bearing a π-extended phenanthridine (3,4-benzoquinoline) unit is presented. The proligand was isolated as the imidazolium salt of chloride (1•HCl), bromide (1•HBr), or hexafluorophosphate (1•HPF6) counterions. These salts can be deprotonated and the carbene installed on silver centres using Ag2O as both a base and a source of metal ion. The resulting Ag(I) complex (1)AgCl can be used in a transmetalation reaction to generate a Pd(II) coordination complex (1)Pd(CH3CN)Cl2. The characterization and photophysical properties of these complexes is presented, along with a demonstration of the utility of (1)Pd(CH3CN)Cl2 in mediating a catalytic C-N cross-coupling reaction for the preparation of the pharmaceutical Piribedil.

Two new Hg(II), {[Hg(phend)2Cl2].(0.5 phend) (1) and [Hg(phend)2Br2].(0.5 phend) (2)} and a new Cd(II) {[CdI2(phend)2] (3)} complexes, containing phenanthridine (phend) ligand, have been synthesized from the reaction of HgCl2 (1), HgBr2(2), and CdI2 (3) with phend, respectively. The complexes were thoroughly characterized by elemental analysis, FT-IR, UV, NMR, and emission spectroscopies. Moreover, single-crystal X-ray diffraction studies were undertaken to examine the coordination geometry of complexes 1-3 in the solid-state. According to X-ray analysis, the complexes 1 (τ4 = 0.77) and 2 (τ4 = 0.74) exhibit distorted tetrahedral geometries and 3 (τ4 = 0.90) shows slightly distorted tetrahedral geometry. So, complexes 1 and 2 have similar structures. However, the emission maximum of complex 1 is stronger than 2, which indicates that the different coordinated counter anions play a significant role in determining the photoluminescence properties of the complexes. Meanwhile, all complexes 1-3 have stronger emissions than free phend ligand in the DMSO solution.

A ratiometric fluorescence phenanthridine sensor (4), functionalised with a pyridine moiety, has been prepared. 4 displayed both fluorescence and absorbance changes for the selective recognition of Hg2+ ions in acetonitrile/water as a solvent in the presence of other relevant interfering metal ions. 4 displayed a noticeable color change of blue to green under exposure to UV light at 365 nm. The binding constant value (Ka) was found to be 2.6198 × 108 M−1 for Hg2+ ions. The probe 4 showed a high selectivity and sensitivity for Hg2+ ions over other interfering competing cations. The ligand 4 interacted with Hg2+ ions to create a 1 : 1 complex, and 1H NMR titration and Job's plot studies further confirmed this mechanism. At the same time, 4 exhibits a high sensitivity to Hg2+ with a detection limit of 49.87 nM. The sensing can be carried out in a wide pH range of 3 to 11. In addition, the sensor 4 can be applied to living bacterial cells for ratiometric visual monitoring of Hg2+ ions by bioimaging. The real time analysis of 4 was also effectively verified by the determination of Hg2+ ions using a paper strip test kit and in different environmental water samples.

We prepared and characterized an array of polarity-sensitive fluorescent dyes (7 and 9a, 9b and 9c). Fluorescent dyes are based on imidazole cores, suitably functionalized with a conjugated push–pull system. The photophysical properties of the synthesized materials were elaborately investigated. These new fluorescent probes showed good fluorecence emission, higher ϕFl values and large Stokes shifts in different organic solvents because of their ICT nature. Furthermore, with aldehyde groups as the recognition sites, all the dyes could act as ratiometric fluorescent sensors towards methanol. The selective ratiometric fluorescence response towards methanol is due to the strong intermolecular H-bonding between the aldehyde unit and methanol. The detection limit of methanol was found to be at the ppm level. Methanol sensing was confirmed using emission spectroscopy, FTIR studies and theoretical calculations. Additionally, these dyes were used for the detection of methanol in biodiesel and in test paper strips.

A series of Fe and Ru coordination complexes supported by bidentate P^N ligands bearing π-extended phenanthridine (3,4-benzoquinoline; PhenLR,R') or quinoline (QuinLH,Ph) N-heterocycles have been synthesized and fully characterized. Tetrahedral monomeric (P^N)FeBr2 and trigonal bipyramidal dimeric ((P^N)FeBr)2(μ-Br)2 complexes were found to be high-spin paramagnets as solids (magnetic susceptibility balance measurements) and in solution (Evans method), while tris-ligated octahedral [(P^N)3M]2+ cations (M = Fe, Ru) are low-spin diamagnets. The electronic environment about each Fe centre was further examined by Mossbauer spectroscopy. The impact of π-extension is evident when comparing the lowest energy absorption bands in the UV-Vis spectra. Contrary to conventional assumptions regarding π-extension, a small hypsochromic shift was observed for the more π-extended phenanthridinyl phosphine-supported Fe(II) complex compared to the analogous quinolinyl complex. Density functional theory (DFT), time-dependent DFT (TDDFT) and charge decomposition analysis (CDA) revealed benzannulation most significantly impacts the character of the lowest energy excitation, rather than appreciably affecting the energies of the frontier orbitals. The impact of electron-transfer on the electronic absorption properties of the π-extended pseudo-octahedral Fe complexes was further explored by spectroelectrochemistry.

Inspired by sanguinarine and chelerythrine, a novel antifungal 2-phenylphthalazin-2-ium scaffold as a simple analogue was designed. Most of the 30 compounds showed excellent inhibition activity against almost all eight phytopathogenic fungi, far superior to sanguinarine and chelerythrine. A third of the compounds were more active than azoxystrobin in most cases. Compounds 26 and 27 showed the highest total activity against all the fungi with EC50 means of ca. 4.6 μg/mL. Fusarium solani showed the highest susceptibility with an EC50 mean of 3.62 μg/mL to 19 compounds. A concentration of 25.0 μg/mL 27 can fully control the Colletotrichum gloeosporioides infection in apples over 9 days. Electron microscopic observations showed that 27 was able to damage the structures of the hypha and cell membrane. The structure-activity relationship showed that the presence of electron-withdrawing groups on the C-ring increases the activity against most of the fungi. Thus, 2-phenylphthalazin-2-ium compounds represent promising leads for the development of novel fungicides.

The reaction of Cd(NO3)2 · 4H2O and Eu(NO3)3 · 6H2O or Tb(NO3)3 · 6H2O with potassium 3,5-di-tert-butylbenzoate (Kbzo) and N-donor ligands (1,10-phenanthroline (phen), 2,4-lutidine (2,4-lut), 3,4-lutidine (3,4-lut), phenanthridine (phtd), 2,3-cyclododecenopyridine (cdpy), acridine (acr)) afforded heterometallic LnCd2 complexes: [EuCd2(bzo)7(EtOH)2(phen)] (2), [LnCd2(bzo)7(2,4-lut)4] (Ln = Eu (3), Tb (4)), [EuCd2(bzo)7(H2O)2(2,4-lut)2] · MeCN (5), [EuCd2(NO3)(bzo)6(EtOH)2(2,4-lut)2] (6), [EuCd2(bzo)7(H2O)(EtOH)(3,4-lut)2] · 5EtOH (7), 3[EuCd2(bzo)7(H2O)2(phtd)2] · 4phtd (8), [EuCd2(bzo)7(EtOH)3(cdpy)] (9), 2[EuCd2-(bzo)2(EtOH)4] · acr (10). The structures of complexes 2, 3, and 5–10 were determined by single-crystal X-ray diffraction. The isostructurality of complexes 3 and 4 was confirmed by powder X-ray diffraction. The structure of the trinuclear {Ln2Cd} metal core is stable and independent of the type of peripheral ligands coordinated to cadmium atoms. Photoluminescent properties of compounds 3 and 4 were studied.

The formation of intramolecular C-N bond represents a powerful strategy in organic transformation as the great importance of N-heterocycles in the fields of natural products and bioactive molecules. This personal account describes the synthesis of cyclic phosphinamidation, benzosultam, benzosulfoximine, phenanthridine and their halogenated compounds through transition-metal-free intramolecular oxidative C-N bond formation. Mechanism study reveals that N-X bond is initially formed under the effect of hypervalent halogen, which is very unstable and easily undergoes thermal or light homolytic cleavage to generate nitrogen radical. Then the nitrogen radical is trapped by the arene to give aryl radical. Rearomatization of aryl radical under the oxidant to provide corresponding N-heterocycle. Under suitable conditions, the N-heterocycles can be further transformed to halogenated N-heterocycles.

A highly stereo- and regioselective synthesis of the core skeleton of hexahydrobenzo[c]phenanthridine-type alkaloids is reported herein for the first time. A wide range of substrate scope, excellent functional group tolerance, and good to excellent yields were observed. This protocol gives very concise and efficient access to the core skeleton of chelidonine alkaloids as compared to the earlier approaches.

The expeditious construction of phenanthridine scaffolds via a Pd/MnO2-mediated C–H arylation/oxidative annulation cascade involving aldehydes, aryl iodides and amino acids is disclosed. This reaction proceeds smoothly involving the formation of multiple chemical bonds with the tolerance of a wide range of functional groups. The control experiments suggest a radical mechanism for C–N bond formation via MnO2-promoted oxidative annulation of imine compounds. The synthetic utility of this transformation has been demonstrated via the straightforward access to bioactive natural alkaloid trisphaeridine and its analogue.

A new series of polycyclic aromatic hydrocarbons (PAHs), namely, various pyrene-fused phenanthridines PyFPs having different substituents were developed as fluorescent emitters for optoelectronic applications. The compounds were synthesized via transition metal-free, base-promoted intramolecular C–C bond formation between pyrene and phenanthridine bridged by imidazole, which facilitated extended π-conjugation throughout the molecule. PyFPs also maintained the vibronic feature characteristic of PAHs with intense blue emission in the solution state, with the spectral maximum at around 425 nm. The absorption spectra of the drop-cast film of PyFPs maintained marginal spectral shifts with respect to that of the solution; however, the fluorescence spectra were quite phenomenal, with the 25 to 107 nm red-shifted spectral maximum showing intense red emission. Fluorescence, electron, and atomic force microscopy images revealed the formation of rod- and flower-like self-assembled supramolecular structures possibly aided by strong intermolecular π–π interactions. Solid-state fluorescence was also observed in the red region with the broad spectra spread over the near-infrared region. The largely red-shifted emission maximum was attributed to the excimer emission in the solid state formed through tailored intermolecular interactions by pyrene and phenanthridine. These have the potential to be used in optoelectronic applications.

A concise synthesis of phenanthridine derivatives is achieved by an iridium-catalyzed direct fusion of oxime ethers and heteroarenes, which is a successful example of a cascade C–H/C–H cross-coupli...

One-pot synthesis of phenanthridine derivatives using appropriately substituted aromatic ortho-bromo N-tosylhydrazones and 2′-aminobenzeneboronic acid pinacol esters is described. In the presence of Pd(amphos)Cl2 catalyst, tosylhydrazone precursors undergo a Suzuki cross-coupling reaction with 2′-aminobenzeneboronic acid pinacol ester derivatives followed by intramolecular condensation to form the corresponding phenanthridines derivatives in one step.

Phenanthriplatin (PtPPH) is a monovalent platinum(II)-based complex with a large cytotoxicity against cancer cells. Although the aqua-activated drug has been assumed to be the precursor for DNA damage, it is still under debate whether the way in which that metallodrug attacks to DNA is dominated by a direct binding to a guanine base or rather by an intercalated intermediate product. Aiming to capture the mechanism of action of PtPPH, the present contribution used theoretical tools to systematically assess the sequence of all possible mechanisms on drug activation and reactivity, for example, hydrolysis, intercalation, and covalent damage to DNA. Ab initio quantum mechanical (QM) methods, hybrid QM/QM′ schemes, and independent gradient model approaches are implemented in an unbiased protocol. The performed simulations show that the cascade of reactions is articulated in three well-defined stages: (i) an early and fast intercalation of the complex between the DNA bases, (ii) a subsequent hydrolysis reaction that leads to the aqua-activated form, and (iii) a final formation of the covalent bond between PtPPH and DNA at a guanine site. The permanent damage to DNA is consequently driven by that latter bond to DNA but with a simultaneous π–π intercalation of the phenanthridine into nucleobases. The impact of the DNA sequence and the lateral backbone was also discussed to provide a more complete picture of the forces that anchor the drug into the double helix.

Although N-alkenoxyheteroarenium salts have been widely used as umpoled synthons with nucleophilic (hetero)arenes, the use of electron-poor heteroarenes has remained unexplored. To overcome the inherent electron deficiency of quinolinium salts, a traceless nucleophile-triggered strategy was designed, wherein the quinolinium segment is converted into a dearomatized intermediate, thereby allowing simultaneous C8-functionalization of quinolines at room temperature. Experimental and computational studies support the traceless operation of a nucleophile, which enables the previously inaccessible transformation of N-alkenoxyheteroarenium salts. Remarkably, the generality of this strategy has been further demonstrated by broad applications in the regioselective C-H functionalization of other electron-deficient heteroarenes such as phenanthridine, isoquinoline, and pyridine N-oxides, offering a practical tool for the late-stage functionalization of complex biorelevant molecules.

Over the past decade, bioorthogonal chemistry that facilitates the efficient conjugation of biomolecules has expanded from the copper-catalyzed alkyne-azide cycloadditions to a multitude of diverse reactions, varying additives and reactional partners, and most often offering better alternatives with faster rates and lower toxicity of employed reactants. Among these, the copper-free strain-promoted cycloaddition reactions have been demonstrated to be more promising, offering a reaction without toxic metal catalysts and with faster inherent kinetic rate constants. The strain-promoted alkyne-nitrone cycloadditions are easily tunable from both the (strained) alkyne and nitrone perspective, both compounds giving the opportunity to modulate the rate of reaction by substituting various positions. Previously, acyclic nitrones have been evaluated in the strain-promoted alkyne-nitrone reactions; however, they were notably prone to hydrolysis. Some five-membered ring endocyclic nitrones developed concomitantly offered the advantage of relatively fast kinetics and better resistance to degradation in aqueous conditions and have been successfully used for labelling of biomolecules in living systems. Herein, we have prepared and studied nitrones inspired by the phenanthridine scaffold that efficiently undergo strain-promoted alkyne-nitrone reactions. Phenanthridine nitrones react fast with strained cyclooctynes with large bimolecular rate constants while maintaining bioorthogonality and resistance to hydrolysis.

The arrangement of small sized molecules with a scaffold structure plays an active role in the fields of sensors and health care. An efficient molecular design strategy for four pyrazole-phenanthridine based D–π–A luminophores, denoted as 2a, 2b, 2c and 2d was developed to investigate the effect of acid on the photo-physical properties of these dyes. Photo-physical studies of the synthesized probes showed distinct absorption and emission under various pH conditions. Theoretical calculations using density functional methods were carried out for understanding the mechanistic aspects of the proton induced fluorescence. The experimentally observed photo-physical properties correlated well with theoretical results. Moreover, probes 2 and 2a can be used to monitor the fluorescence changes in E. coli cells under different pH conditions.

A series of indole-based helicenes, namely, 15-hexyl-15H-tetraphenyl[1,2-e]indole (HTPI), 14-hexyl-14H-benzo[4',5']thieno [2',3':7,8]naphtha[1,2-e]indole (HBTNI), 7-hexyl-7H-indolo[5,4-k] phenanthridine (HIPD) and 3-hexyl-3H-phenanthro[4,3-e]indole (HPI) were successfully synthesized by three- or four-step reactions. They exhibited good solubility and high thermal stability of Td =247, 388, 294 and 251 °C, respectively. These compounds emit violet-blue light with maximum emission peaks at 415, 397, 397 and 391 nm in hexane. Among them, HBTNI had excellent thermal stability, narrow and sharp emission peaks, and highest photoluminescence quantum yield (0.32). Thus, HBTNI was an ideal candidate for the violet-blue emitters of OLEDs. Furthermore, the four compounds had two-photon absorption and two-photon excited fluorescence. HTPI showed the maximum TPA with the TPA cross-section (δ) of 171.5 GM at 770 nm. They were rare examples of helicenes with both violet-blue emission and TPA.

3-Arylpropynenitriles are readily annulated with phenanthridine in the KOH/H2O/MeCN system at room temperature to afford 4-aryl-1,13b dihydropyrimido[1,2-f]phenanthridin-2-ones. The moderate yield of the products can be rationalized by the anionic oligomerization of an intermediate zwitterion adduct of the reactants. The reaction represents a single-stage access to a new family of pharmaceutically prospective compounds.

Representatives of the new heterocyclic system, pyrimido[5’,4’:3,4]pyrrolo[1,2-f]phenanthridine, were obtained via the intramolecular C–H-arylation of 6-aryl-5-(2-bromophenyl) pyrrolo[3,4-d]pyrimidine-2,4-diones catalyzed by palladium complexes with N-heterocyclic carbene ligands (Pd/NHC).

By making use of a dual-chelation-assisted strategy, a completely regiocontrolled oxidative C-H/C-H cross-coupling reaction between an N-acylaniline and a benzamide has been accomplished for the first time. This process constitutes a step-economic and highly efficient pathway to 2-amino-2'-carboxybiaryl scaffolds from readily available substrates. A Cp*-free RhCl3 /TFA catalytic system was developed to replace the [Cp*RhCl2 ]2 /AgSbF6 system generally used in oxidative C-H/C-H cross-coupling reactions between two (hetero)arenes (Cp*=pentamethylcyclopentadienyl, TFA=trifluoroacetic acid). The RhCl3 /TFA system avoids the use of the expensive Cp* ligand and AgSbF6 . As an illustrative example, the procedure developed herein greatly streamlines the total synthesis of the naturally occurring benzo[c]phenanthridine alkaloid oxynitidine, which was accomplished in excellent overall yield.

A silver-mediated free-radical cascade cyclization of isocyanides with potassium alkyl trifluoroborates was developed. The procedure tolerates a series of functional groups, including chloro, bromo, ester, ketone, and amide. Additionally, it is not sensitive to steric hindrance. Thus, this reaction represents a very useful strategy for the production of 6-alkylated phenanthridine derivatives. The addition of alkyl radical to the isonitrile, followed by a radical aromatic cyclization, is involved in this transformation.

2-(2-Bromophenyl)-4,5-diphenyl-1H-imidazole was used as an aryl halide to underwent α-arylation with 1,3-cyclohexanedione first, and then a nucleophilic addition and dehydration to give 2,3-diphenyl-6,7-dihydroimidazo[1,2-f]phenanthridin-8(5H)-one derivatives in good yields. This one-pot CuI-catalyzed procedure provided an efficient method for the synthesis of fused tetracyclic heterocycles containing both imidazole and phenanthridine moieties.

A new and simple fluorescent probe bearing mono-sulfur (1) and tetra-sulfur (2) tetrahydrodibenzo phenanthridine derivatives were synthesized and examined for their cation recognition abilities towards different cations in aqueous acetonitrile solution and paper strips. Both the probes showed high selectivity and sensitivity with strong affinity towards Hg2+ ions over other cations, such as Cu2+, Ca2+, Co2+, Cd2+, Pb2+, Zn2+, Ni2+, Mg2+, Mn2+, Al3+, Fe3+, La3+, Ag+, K+, Na+ and Li+. The binding stoichiometry ratios of 1–Hg2+ and 2–Hg2+ are recognized as 1 : 1 according to the UV-Vis absorption spectra, fluorescence measurements and computational (DFT) studies, and the possible binding mode of these receptors with Hg2+ is also proposed. The limit of detection with Hg2+ cation was found to be as low as 0.91 nM and 0.041 nM for probes 1 and 2, respectively. The results clearly indicate that the synthesised tetrahydrodibenzo phenanthridine derivatives 1 and 2 could be used as excellent chemosensors for Hg2+ detection in biological and environmental samples.

Pharmaceutically important benzo[c]phenanthridine alkaloid chelerythrine (CHL) exists in charged iminium [CHL (I)] and neutral alkanolamine [CHL (A)] forms depending on pH. The mechanism of interaction of these two isoforms with human serum albumin (HSA) was investigated by employing various spectroscopic techniques, isothermal titration calorimetry (ITC) and molecular docking simulation. The primary objective was to corroborate the binding position of CHL within HSA as well as to investigate the comparative binding strength between CHL (I) and CHL (A). Spectroscopic investigation revealed that the alkanolamine form of CHL undergoes stronger association with HSA in comparison to its iminium counterpart. However, such a mode of binding induces some unfolding of the protein secondary and tertiary structures detectable in the circular dichroism (far-UV CD) spectra resulting in a concomitant decrease in the α-helical content of the protein. From the site selective competitive binding assay, we found that both iminium and alkanolamine forms of CHL bind at Sudlow's site I in subdomain IIA of HSA. Electrostatic interactions play the major role in CHL (I) binding whereas hydrophobic interactions are the main cause behind the stabilization of the CHL (A)–HSA complex. In addition, molecular docking specified that hydrogen bonding was also present in both cases with His 242 residue in site I. Thermodynamic parameters obtained from ITC showed that the binding of CHL (I) with HSA was favoured by a negative enthalpy change and opposed by a negative entropy change, whereas the association of CHL (A) with HSA was characterized by both positive enthalpy and entropy changes. FRET analysis showed that the binding distance between CHL (I) and CHL (A) with HSA (Trp 214) was most favourable (r = 2.32 and 2.05 nm respectively) for quenching to occur.

A concise two-step operation of α-amination of aldehydes and subsequent Friedel-Crafts/Prins-type cyclization towards accessing tetrahydrobenzo[c]phenanthridine and related structures was developed. The reaction displayed a broad substrate scope and good tolerance to a variety of substituents such as different aromatic heterocyclic rings. In addition, the effectiveness of this protocol was also demonstrated in the formal synthesis of homochelidonine and chelamidine.

A new 5-(furan-2-yl)-7, 8, 13, 14-tetrahydrodibenzo[a,i]phenanthridine (4a) was designed and synthesized for the highly selective determination of Cr3+ over other examined metal ions in semi-aqueous medium. The sensor probe 4a displays significant colorimetric and fluorometric recognition of Cr3+ ion due to the coordination of chromium ion to the electron rich furan oxygen atom and pyridine nitrogen atom of 4a, which induces intramolecular charge transfer character. Compound 4a, on adding Cr3+, exhibited excellent advantages such as high blue emission, fast response time (30 s) and low detection limit (142 nM). The binding mechanism of 4a with Cr3+ was established by FTIR analysis, 1H NMR titration experiment, HRMS and Job’s plot analysis. Inspired by these considerable sensing properties, compound 4a has been successfully applied for detection of Cr3+ in environmental water samples and fluorescence bio-imaging in E-coli bacteria with satisfactory results.

A series of highly luminescent [Pt(NˆCˆCˆN)] emitters (ZPt1, ZPt2 and ZPt3) based on pyrazolo[1,5- f ]phenanthridine-containing ligands were designed and synthesized. These Pt(II) complexes demonstrated extremely high thermal stabilities with the 5% weight-reduction temperatures over 450 °C due to the incorporation of the rigid pyrazolo[1,5- f ]phenanthridine motif and the robustness of the tetradentate coordination framework. These Pt(II) complexes have the same coordination set (pyridineˆbenzeneˆbenzeneˆpyrazole) but with slightly different linkage between coordination groups. Within ZPt1 and ZPt2, pyridine and the neighboring benzene groups are separated by oxygen and aniline, respectively. In ZPt3, pyridine group is rigidly grafted on the carbazole unit. The effect of the different linkages on the frontier orbital energies, the photophysical and electroluminescent properties of ZPt1-ZPt3 was investigated systematically. Organic light emitting diodes (OLEDs) based on these Pt(II) complexes were fabricated with typical device structure. The Pt(II) complexes displayed intense electroluminescence in the blue to yellowish green spectral region. Among the three Pt(II) complexes, the 3-(pyridin-2-yloxy)phenoxy-based ZPt1 compound showed the highest electroluminescence performance with the maximum CE, PE, and EQE of 58.0 cd A −1 , 51.6 lm W −1 , and 16.4%, respectively.

The title compound was synthesized using a novel one-pot method under mild conditions and fully characterized using NMR, ESI–MS and SXRD. The supra­molecular structure of the title compound is defined by a combination of C—H⋯N and π–π inter­actions., The preparation of the title compound, C26H25N, was achieved by the condensation of an ethano­lic mixture of benzaldehyde, cyclo­hexa­none and ammonium acetate in a 2:1:1 molar ratio. There are two crystallographically independent mol­ecules in the asymmetric unit. The two cyclo­hexyl rings adopt an anti-envelope conformation with the benzyl moiety adopting a cis conformation with respect to the nitro­gen atom of the phenanthridine segment. In the crystal, mol­ecules are linked through C—H⋯N inter­actions into hydrogen-bonded chains that are further arranged into distinct layers by weak offset π–π inter­actions.

A dinickel imido complex was synthesized using a redox-active naphthyridine-diimine supporting ligand. Upon coordination of an external ligand, the Ni2 core was disrupted, triggering an aromatic C-H activation reaction to generate a Ni2 (μ-NHAr)(Ar) species. This intermediate is capable of liberating free carbazole and phenanthridine products upon heating or treatment with excess tBuNC. Collectively, these studies establish a kinetically facile 1,2-addition mechanism for C(sp2 )-H activation, taking advantage of cooperative reactivity between two Ni centers.

A ruthenium(II)-catalyzed cross-ring (5+1) annulation between 2-aminobiphenyls and activated olefins is disclosed for succinct synthesis of valuable phenanthridine scaffolds. The protocol avails a common organic functional group, free amine, as a directing group and represents a unique combination of C–H activation/annulation/C–C bond cleavage cascade that bodes well in the production of bioactive alkaloids including trisphaeridine and bicolorine.

The ability to tune the band-edge energies of bottom-up graphene nanoribbons (GNRs) via edge dopants creates new opportunities for designing tailor-made GNR heterojunctions and related nanoscale electronic devices. Here we report the local electronic characterization of type II GNR heterojunctions composed of two different nitrogen edge-doping configurations (carbazole and phenanthridine) that separately exhibit electron-donating and electron-withdrawing behavior. Atomically resolved structural characterization of phenanthridine/carbazole GNR heterojunctions was performed using bond-resolved scanning tunneling microscopy and noncontact atomic force microscopy. Scanning tunneling spectroscopy and first-principles calculations reveal that carbazole and phenanthridine dopant configurations induce opposite upward and downward orbital energy shifts owing to their different electron affinities. The magnitude of the energy offsets observed in carbazole/phenanthridine heterojunctions is dependent on the length of the GNR segments comprising each heterojunction with longer segments leading to larger heterojunction energy offsets. Using a new on-site energy analysis based on Wannier functions, we find that the origin of this behavior is a charge transfer process that reshapes the electrostatic potential profile over a long distance within the GNR heterojunction.

The structural and photophysical properties of three sets of luminescent copper complexes of the form [(P^N)2Cu]X are presented. Here, P^N represents a bidentate ligand based on phenanthridine (3,4-benzoquinoline) incorporating a phosphine unit at the 4-position, of which three examples are investigated, namely 4-(diphenylphosphino)phenanthridine (L1), 4-(diphenylphosphino)-2-methylphenanthridine (L2) and 2,6-dimethyl-4-(diphenylphosphino)phenanthridine (L3). For each P^N-coordinating ligand, the corresponding homoleptic copper(I) complex (1X, 2X, 3X) has been prepared as both the hexafluorophosphate and tetraphenylborate salt (X = PF6− or BPh4−). The identity of the counterion has a profound and unexpected impact on the emission properties of the powder samples – but only for complexes of ligands bearing methyl substituents close to the metal (3X). The synergistic effect of combining inter-ion interactions and ligand design enables emission tuning from orange to yellow, in the opposite (hypsochromic) direction compared to employing either strategy on its own. These effects can be attributed to differences in molecular packing, in particular to the combined impact of ligand structure and inter-ionic interactions on distortions in the excited state relative to the ground state. The results have been interpreted with the help of density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations.

The potential anticancer drug phenanthriplatin, [cis-(NH3)2(phenanthridine)Cl]+, forms supramolecular complexes with cucurbit[n]urils (CB[n], n = 7 or 8), β-cyclodextrin and para-sulfonatocalix[4]arene (sCX[4]) as determined by 1H NMR spectroscopy and molecular modeling. The results show that cucurbit[7]uril binds over the long arm of the drug, where hydrophobic effects and two hydrogen bonds stabilise binding. For cucurbit[8]uril, two phenanthriplatin molecules can bind simultaneously within the macrocycle’s cavity. Unfortunately, Na+ was able to displace the drug from both CB[7] and CB[8] making the macrocycles unsuitable as delivery vehicles for phenanthriplatin. Drug binding to β-cyclodextrin occurs at the portal of the macrocycle with no part of the phenanthriplatin located within the cavity. Phenanthriplatin binding to sCX[4] occurs in a 2-to-1, macrocycle-to-drug, ratio with the formation of a capsule-like complex where each sCX[4] binds over opposing ends of the drug. The results indicate that para-sulfonatocalix[4]arene is the only suitable macrocycle of the four studied for further research into phenanthriplatin drug delivery.

Three blue-emitting Pt(II) complexes (Pt1, Pt2 and Pt3) supported by imidazo[1,2-f]phenanthridine-containing tetradentate ligands have been designed and prepared. A fused ring system, imidazo[1,2-f]phenanthridine, was introduced into these complexes to minimize the vibration and rotation of the ligand due to its rigidity, and the incorporation of this robust motif led to the high thermal stability of the resulting complexes. In addition, this efficient bidentate possesses high triplet energy (ET) to allow the preparation of blue-emitting complexes. A bulky mesityl group was attached to this rigid unit to reduce the strong intermolecular interaction and suppress the formation of an excimer in the solid state. Imidazo[1,2-f]phenanthridine was connected with three different pyridine^benzene bidentates to give the corresponding tetradentate ligands (L1, L2 and L3). In L1, the pyridine group was directly bonded to an N atom of a carbazole group; while in L2 and L3, the pyridine unit was linked to a benzene group via oxygen and spiro linkages, respectively. The introduction of a heteroatom linkage and spiro linkage into these tetradentate ligands would be effective in breaking the conjugation, leading to a wide bandgap and high ET. Despite the different linkages applied in the pyridine^benzene bidentates, complexes Pt1–Pt3 showed similar photoluminescence spectra with an intense emission peak at 460 nm. Organic light-emitting diodes (OLEDs) based on these complexes were fabricated by vacuum deposition with the typical device configuration. All these complexes showed blue electro-phosphorescence at various doping ratios. Among these Pt(II) complexes, Pt1 showed the highest OLED performance with a maximum CE, PE, and EQE of 36.5 cd A−1, 33.1 lm W−1, and 16.2%, respectively, with the CIE coordinates of (0.18, 0.32).

A new group of multifunctional ligands for DNA and RNA were prepared, comprising phenanthridinium and triazolyluracil connected by various aliphatic or peptide linkers. The peptide linker conjugates showed at least one order of magnitude higher affinity in comparison to aliphatic analogues, which was attributed to peptide-specific hydrophobic and hydrogen bonding interactions within DNA/RNA binding sites. Particularly, a peptide linker conjugate with lysine residue showed selectivity toward poly rA–poly rU, as well as toward poly U, both characterized by strong affinity and a selective fluorescence response. Negligible cytotoxicity of compounds additionally supported their possible applications as fluorimetric probes in laboratory use.

Flash vacuum pyrolysis (FVP) of benz[a]azulene yields phenanthrene and 2-ethynylbiphenyl. FVP of cyclohepta[b]indole similarly yields phenanthridine and 2-cyanobiphenyl. The reversibility of the reactions is demonstrated by FVP of 2-ethynylbiphenyl and 2-isocyanobiphenyl. All the observed reactions are in accord with the norcaradiene-vinylidene mechanism of the azulene-naphthalene rearrangement, whereas other proposed mechanisms are ruled out.

A novel visible-light-induced trifluoromethylation of isonitrile-substituted methylenecyclopropanes is developed. A range of substituted 6-(trifluoromethyl)-7,8-dihydrobenzo[k]phenanthridine derivatives are readily furnished by this newly developed tandem trifluoromethylation reaction with moderate to good yields. This reaction allows the direct formation of two six-membered rings and three new C-C bonds including the C-CF3 bond under the irradiation by visible light.

We have developed a Cu(II) -, Ag(I) -, and NaOTf-mediated intramolecular quaternization by arylation reactions to synthesize a variety of N-heterocyclic carbene (NHC) precursors with a benzene-fused backbone. The methodology also provides a convenient alternative route for the synthesis of 6-H-phenanthridine derivatives. A novel silver-NHC complex was prepared by treatment of Ag2 O with the free carbene, which was in situ prepared from the deprotonation of a representative quinazolinonium salt.

A versatile one-step two-component cyclization to build new tetracyclic nitrogen heterocycles is described. Ortho-methylhetarenecarbonitrile components were condensed with aldehydes to access a large library of differently substituted ring systems. The heterocyclic core can be easily modified by variation of the position of the endocyclic nitrogen atom in the o-methylhetarenecarbonitrile substrate. The manner of the nucleophilic attack that leads to the condensation can be triggered by different electron-density distribution in the molecule induced by the position of the nitrogen atom. Taking this into account, there is an electronic preference that leads to either pyridophenanthrolines or the corresponding pyridoazacarbazoles as the main products. We demonstrate the high antitumor potential of some of our synthesized heterocycles, which is strongly dependent on the substitution pattern introduced through the aldehyde component. The position and number of endocyclic nitrogen atoms play an important role regarding cytotoxicity of the studied compounds.