Bismuth Centers Research Articles

Photoassisted ionization spectroscopy of few implanted bismuth orbitals in a silicon-on-insulator device

The electrically detected orbital spectrum of a mesoscopic silicon device containing a small number of donors has been investigated. The device was fabricated on silicon-on-insulator with an optically active channel containing 6×105 substitutional bismuth centers introduced by ion implantation. The 1s(A1)→2p± orbital transition at the energy associated with isolated bismuth donors was detected via a change in photocurrent when illuminated by THz light from a free electron laser. The spectral dependence on bias, temperature, and laser intensity is explored to determine optimum conditions for detecting orbital transitions in smaller devices with fewer donors. These results suggest that photo-induced impact ionization can offer a route for the spectroscopic detection of few impurities providing a useful tool for the development of solid-state quantum technologies.

Syntheses, Polymorphic Transformations, and Functions of Ionic Crystals Based on Mononuclear Bismuth(III) Complexes and Polyoxometalates

AbstractThe controlled assembly of molecules, ions, and ligands as building blocks based on crystal engineering leads to various functional crystalline solids. In particular, polyoxometalates (POMs), which are anionic metal oxide clusters, have been a popular motif in crystal engineering. To revisit simple mononuclear metal complexes as counter cations of POMs, seven ionic crystals based on Keggin‐ or Dawson‐type POMs with mononuclear bismuth(III) complexes as counter cations were synthesized. The bismuth(III) center exhibited triangular dodecahedron, square antiprism, or pseudo‐cubic eight‐coordination geometries, with dimethyl sulfoxide or N,N‐dimethylformamide as ligands. The ionic crystals showed polymorphic transformation depending on the synthetic or recrystallization conditions. As a method for exploring functionality, proton conductivities of the ionic crystals were measured under humidified conditions. The ionic crystals with high porosity, tertiary amine moieties, or coordination water exhibited high proton conductivities, and large activation energies indicate that protons are transferred mainly with water molecules via the vehicle mechanism.

Structural manifestations and biological screening for newly synthesized heteroleptic bismuth(V) bis-carboxylates

Six new heteroleptic tri-organobismuth(V) complexes (1-6), of general formula, R3Bi(OOCR')2 where R = C6H5 (1-3), p-CH3C6H4 (4-6) and R' represents deprotonated 2-(methylthio)nicotinic acid (1, 4); 3-thiophenecarboxylic acid (2, 5) and 4-chlorosalicylic acid (3, 6) have been synthesized and characterized by FT-IR, NMR (1H, 13C) and single crystal XRD techniques in addition to elemental analyses. The solid-state structure for 3 has also been elucidated by crystallographic data, manifesting its distorted trigonal bipyramidal molecular geometry with a five-coordinate bismuth center. The carboxylate ligand(s) assume a monodentate coordination mode as predicted by IR and then confirmed by XRD data. The antibacterial, antifungal and antileishmanial potential for 1-6 have been evaluated and the preliminary screening data suggest significant to average biological activities. The antileishmanial activity data manifest comparatively lower IC50 value for 5 than the standard drug. A comprehensive study for 1-6 was also undertaken to testify their stability both in solid and solution phases as well as in leishmanial culture M199, which demonstrate high degree of stability that may ensure their significant antileishmanial effect. The % viability values of the organobismuth(V) bis-carboxylates highlight their role as significantly effective compounds, having potential candidature for future drug discovery and development processes.

Unveiling the Electronic Structure of the Bi(+1)/Bi(+3) Redox Couple on NCN and NNN Pincer Complexes.

Low-valent group 15 compounds stabilized by pincer ligands have gained particular interest, given their direct access to fine-tune their reactivity by the coordination pattern. Recently, bismuth has been employed in a variety of catalytic transformations by taking advantage of the (+1/+3) redox couple. In this work, we present a detailed quantum–chemical study on the electronic structure of bismuth pincer complexes from two different families, namely, bis(ketimine)phenyl (NCN) and triamide bismuthinidene (NNN). The use of the so-called effective oxidation state analysis allows the unambiguous assignation of the bismuth oxidation state. In contrast to previous studies, our calculations suggest a Bi(+1) assignation for NCN pincer ligands, while Bi(+3) character is found for NNN pincer complexes. Notably, regardless of its oxidation state, the central bismuth atom disposes of up to two lone pairs for coordinating Lewis acids, as indicated by very high first and second proton affinity values. Besides, the Bi–NNN systems can also accommodate two Lewis base ligands, indicating also ambiphilic behavior. The effective fragment orbital analysis of Bi and the ligand allows monitoring of the intricate electron flow of these processes, revealing the noninnocent nature of the NNN ligand, in contrast with the NCN one. By the dissection of the electron density into effective fragment orbitals, we are able to quantify and rationalize the Lewis base/acid character.

Microstructure of bismuth centers in silicon before and after irradiation with 15 MeV protons

A decrease of two-gamma annihilation rate of a positron in a strong spin–orbit field of the annihilation site of bismuth impurity center 209Bi (J = 9/2) in silicon with natural isotope composition was revealed (J is the nuclear spin). This decrease was observed along with increasing occupancy of Bi donor states (binding energy E{Bi} ≈ 69 meV). Atoms of 29Si (J = 1/2) isotope are involved in spin interactions of positron with Bi impurity centers. The growth of occupancy of Bi donor states inhibits two-gamma annihilation rate. The estimated cross-section of positron trapping by the Bi impurity center is σ + ≈ (1.23–1.5) × 10−13 cm2. Together with this surprisingly large value, the integral rate of two-gamma annihilation in a hypothetical polyelectron system of the Bi impurity center is by a factor of just Δ ∼ 2.18 higher compared to the magnitude ≈2.09 × 109 s−1 known for elemental isolated polyelectron, (e−e+e−). Possible formation of the positron-containing exciton-like states, (e+)D 0 X (D = Bi, P) is also discussed. Irradiation of material with 15 MeV protons results in decreasing the factor Δ by ∼11% due to forming the radiation complex in which Bi atom is in an open volume ambient it. Such complex is suggested to have D 3d symmetry and be the deep donor. Low-temperature measurements of both the positron annihilation rate and Hall effect have been applied for studying the isochronal annealing of these point radiation defects which were found to be thermally stable up to ∼370 °C; they can be annealed at ∼430 °C – 470 °C. According to available data of ab initio cluster calculations, the complex of Bi atom with a simulated vacancy has D 3d symmetry with the energy gain ∼0.92 eV, thus indicating qualitative agreement between experimental and theoretical data.

Carbodicarbene Bismaalkene Cations: Unravelling the Complexities of Carbene versus Carbone in Heavy Pnictogen Chemistry.

We report a combined experimental and theoretical study on the first examples of carbodicarbene (CDC)‐stabilized bismuth complexes, which feature low‐coordinate cationic bismuth centers with C=Bi multiple‐bond character. Monocations [(CDC)Bi(Ph)Cl][SbF6] (8) and [(CDC)BiBr2(THF)2][SbF6] (11), dications [(CDC)Bi(Ph)][SbF6]2 (9) and [(CDC)BiBr(THF)3][NTf2]2 (12), and trication [(CDC)2Bi][NTf2]3 (13) have been synthesized via sequential halide abstractions from (CDC)Bi(Ph)Cl2 (7) and (CDC)BiBr3 (10). Notably, the dications and trication exhibit C⇉ Bi double dative bonds and thus represent unprecedented bismaalkene cations. The synthesis of these species highlights a unique non‐reductive route to C−Bi π‐bonding character. The CDC‐[Bi] complexes (7–13) were compared with related NHC‐[Bi] complexes (1, 3–6) and show substantially different structural properties. Indeed, the CDC ligand has a remarkable influence on the overall stability of the resulting low‐coordinate Bi complexes, suggesting that CDC is a superior ligand to NHC in heavy pnictogen chemistry.

Carbodicarbene Bismaalkene Cations: Unravelling the Complexities of Carbene versus Carbone in Heavy Pnictogen Chemistry

AbstractWe report a combined experimental and theoretical study on the first examples of carbodicarbene (CDC)‐stabilized bismuth complexes, which feature low‐coordinate cationic bismuth centers with C=Bi multiple‐bond character. Monocations [(CDC)Bi(Ph)Cl][SbF6] (8) and [(CDC)BiBr2(THF)2][SbF6] (11), dications [(CDC)Bi(Ph)][SbF6]2 (9) and [(CDC)BiBr(THF)3][NTf2]2 (12), and trication [(CDC)2Bi][NTf2]3 (13) have been synthesized via sequential halide abstractions from (CDC)Bi(Ph)Cl2 (7) and (CDC)BiBr3 (10). Notably, the dications and trication exhibit C Bi double dative bonds and thus represent unprecedented bismaalkene cations. The synthesis of these species highlights a unique non‐reductive route to C−Bi π‐bonding character. The CDC‐[Bi] complexes (7–13) were compared with related NHC‐[Bi] complexes (1, 3–6) and show substantially different structural properties. Indeed, the CDC ligand has a remarkable influence on the overall stability of the resulting low‐coordinate Bi complexes, suggesting that CDC is a superior ligand to NHC in heavy pnictogen chemistry.

Comparative study of luminescent properties of Bi1-xPrxGeSbO6 and La1-xPrxGa0.5Sb1·5O6 (x = 0–0.5) solid solutions with rosiaite structures

In this work, Bi1-xPrxGeSbO6 (x = 0–0.5) solid solutions were synthesized, and the corresponding properties were compared to those of La1-xPrxGa0.5Sb1·5O6. The lattice parameters of the La1-xPrxGa0.5Sb1·5O6 solid solutions decrease linearly as the activator concentration increases. This linear reduction is only observed for the a parameter for Bi1-xPrxGeSbO6. Parameter c shows non-linear growth, which is related to the structural features of BiGeSbO6. Increasing the activator content leads to a decrease in the particle size, which is 0.5–8 μm for Bi1-xPrxGeSbO6. The influence of the host composition on the spectral-luminescent properties of the solid solutions was determined. The difference in the phonon frequencies of BiGeSbO6 and LaGa0.5Sb1·5O6 leads to different luminescence quenching processes for Pr3+ ions. Interactions between Pr3+ ions and Bi3+ were observed for Bi1-xPrxGeSbO6 solid solutions. These processes give rise to changes in the ratios of the luminescence bands of these ions. All the bismuth-containing solid solutions are characterized by the appearance of an additional band in the spectrum related to the luminescence of the bismuth centres of the BiGeSbO6 host. An evaluation of the colour coordinates (CIE 1931) of the Bi1-xPrxGeSbO6 luminescence showed that the colour of the radiation depends on the praseodymium content: as the praseodymium content increases, the luminescence changes from orange (x = 0.005, 0.01) to yellow-green (x = 0.05–0.5). Broadband thermal emission is observed for Bi0.5Pr0.5GeSbO6 under laser excitation with λ = 457 nm and a power density of J = 6 kW/cm2.

Structural and biological features of bismuth(III) halide complexes with heterocyclic thioamides

Ten novel bismuth(III) halide complexes of [Bi(L)X3]n, [Bi(L)2×3]2, and [Bi(L)3×3] structural types were synthesized, in which L: 5-ethoxy-2-mercaptobenzimidazole, 5‑methoxy-2-mercaptobenzimidazole and N-methylbenzothiazole. Bismuth(III) halide complexes 1–10 were characterized by melting point, elemental analysis, molar conductivity, FT-IR, FT-Raman, UV-Visible, 1H and 13C NMR spectroscopic techniques, as well as by the Thermogravimetric-Differential Thermal Analysis (TG-DTA). The crystal structures of complexes 1–10 were determined by using single crystal X-ray diffraction study. The results show that the bismuth(III) complexes exist as monomer (4), doubly-bridged dimer (1–3 and 5–9), and edge-sharing polymer (10), in which the central bismuth atom is a six-coordinated and adopts distorted octahedral geometries. We report here, for the first time, cis-sulfur, cis-halide arrangement of the doubly-bridged dimer bismuth(III) complexes. The intermolecular interactions in bismuth(III) complexes play a very important role in the supramolecular architecture. A detailed analysis of the intermolecular interactions has been performed as based on the Hirshfeld surfaces and their associated two-dimensional fingerprint plots. Bismuth(III) halide complexes 1–10 and their free ligands have been screened for antimicrobial activity against two Gram negative bacteria (Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853) and two Gram positive bacteria (Staphylococcus aureus ATCC 25923 and Enterococcus faecalis ATCC 29212). The influence of complexes 1–10 and the free ligands on the catalytic peroxidation of the linoleic acid by the enzyme lipoxygenase (LOX) has been determined experimentally and theoretically.

Electrophilic Organobismuth Dication Catalyzes Carbonyl Hydrosilylation.

Bismuth compounds are gaining importance as potential alternatives to transition-metal complexes and electron deficient lighter p-block compounds in homogeneous catalysis. Computational analysis on the two-coordinate [(Me2 NC6 H4 )Bi]2+ possessing three electrophilic sites is experimentally evidenced by the isolation of [{Me2 NC6 H4 }Bi{OP(NMe2 )3 }3 ][B(3,5-C6 H3 Cl2 )4 ]2 . These observations led us to generate dicationic organobismuth catalyst, [(Me2 NC6 H4 )Bi(L)3 ]2+ (L=aldehyde/ketone), evidenced by NMR spectroscopy in solution and by single-crystal X-ray diffraction in the solid state. It efficiently catalyzes hydrosilylation of aldehydes and ketones resulting in silyl ethers as the only products in high yields. Our investigations support a carbonyl activation mechanism at the bismuth center followed by Si-H addition.

High Lewis Acidity at Planar, Trivalent, and Neutral Bismuth Centers

Geometric perturbation away from classical structures can engender unusual frontier MO situations leading to high Lewis acidity. Recently we reported a T-shaped bismuth triamide, which exhibited pl...

Bismuth(III) Flavonolates: The Impact of Structural Diversity on Antibacterial Activity, Mammalian Cell Viability and Cellular Uptake.

A series of homoleptic and heteroleptic bismuth(III) flavonolate complexes derived from six flavonols of varying substitution have been synthesised and structurally characterised. The complexes were evaluated for antibacterial activity towards several problematic Gram-positive (Staphylococcus aureus, methicillin-resistant Staphylococcus aureus (MRSA), and vancomycin-resistant Enterococcus (VRE)) and Gram-negative (Escherichia coli, Pseudomonas aeruginosa) bacteria. The cell viability of COS-7 (monkey kidney) cells treated with the bismuth flavonolates was also studied to determine the effect of the complexes on mammalian cells. The heteroleptic complexes [BiPh(L)2 ] (in which L=flavonolate) showed good antibacterial activity towards all of the bacteria but reduced COS-7 cell viability in a concentration-dependent manner. The homoleptic complexes [Bi(L)3 ] exhibited activity towards the Gram-positive bacteria and showed low toxicity towards the mammalian cell line. Bismuth uptake studies in VRE and COS-7 cells treated with the bismuth flavonolate complexes indicated that Bi accumulation is influenced by both the substitution of the flavonolate ligands and the degree of substitution at the bismuth centre.

Coordination polymers incorporating Bi(III) and 2,4,6-pyridine tricarboxylic acid and its derivatives: Synthesis, structure and topology

Bi(III) as its oxide combined with 2,4,6-pyridine tricarboxylic acid, H2pdc-COOH, and various pyridine-derived additives in dimethylformamide (dmf) under solvothermal conditions produced three novel bismuth coordination polymers, {[Bi(μ-pdc-COO)2][NH2Me2]3}n, 1, {[Bi(μ-pdc-COO)2][C5H7N2]3·C5H6N2}n, 2, and {[Bi2(μ-pdc-COO)2(μ-pdc-COOH)(pdc-COOH)][NH2Me2]4·2dmf·NHMe2}n, 3. The anionic coordination network topologies are two-dimensional, chains-of-loops and ladders, respectively, but the local 8-coordinate environments about the bismuth(III) centres are in each case between that of a square antiprism and that of a hexagonal bipyramid. When the 4-carboxy substituent in H2pdc-COOH is replaced by another potentially coordinating substituent to give 4-R-2,6-pyridine dicarboxylic acid, H2pdc-R (R = OH, NH2, Cl), the salts obtained contain discrete centrosymmetric dinuclear 8-coordinate bismuth anions with either double O-bridges between the metal centres, [Bi2(μ-pdc-R)2(pdc-R)2(dmf)2][NH2Me2]2 (R = OH, NH2), 4 and 5, or double carboxylate bridges with one long Bi–O bond, [Bi2(μ-pdc-NMe2)2(pdc-NMe2)2(dmf)2][NH2Me2]2, 6 (R = Cl, but replaced by dimethylamine during the reaction). The structures and supramolecular networks of 1–6 are described and compared as an exploration of alternatives to the conventional carboxylate-based organic linking units.

Chiral Ferrocenyl-Bismuthines containing N/O donor pendant arm: Syntheses and molecular structures

Some new chiral substituted ferrocenyl bismuthines CpFe(2-[Me2NCH(R)]C5H3)BiPhCl where R = H (1) or Me (2) and CpFe(2-[Me2NCH(R)]C5H3)BiPh2 where R = H (3) or Me (4) (Cp = cyclopentadienyl) containing a Rac-2-[(Me2NCH(R)] pendant arm on the ferrocenyl ring were synthesized. Nucleophilic substitution reaction of mono ammonium salt Rac-{[CpFe{2-(Me3N+CH2)C5H3}BiPh2][I−] (5) by o-hydroxyacetaphenone, salicyladehyde, N-methylpiperazine and 4′- aminobenzo-15-crown-5 in acetonitrile gave new ferrocenyl bismuthines [CpFe{2-(RCH2)C5H3}BiPh2] where R = OC6H4-2-C(O)Me (6), OC6H4-2-C(O)H (7), N(CH2CH2)2NMe (8) and NHC6H4-3,4-O-cyclo{(CH2)2-O}4 (9) respectively with N or O containing pendant arm. All the new compounds were characterized by 1H NMR, 13C NMR, FAB+, and High-Resolution Mass Spectrometry. All the compounds presented in this work present planar chirality because of 1,2-disubstituted ferrocene. In the solid-state, the presence of the ferrocenyl group influences the stereoelectronic properties in the molecule and Bi···N or Bi···O hypervalent interaction could not be observed in compounds with BiPh2 fragment while this interaction was observed in compounds with BiPhCl fragment. For compounds (1)-(4), (6)-(8) and (10), NMR spectra obtained at different temperatures show the association and/or dissociation of hypervalent N···Bi coordination in these compounds. Molecular structures of compounds (1), (2) and (10) show distorted pseudo-trigonal bipyramidal geometry (see-saw structure) at bismuth center with intramolecular Bi···N hypervalent interaction while (6) and (7) present a distorted pseudo-trigonal pyramidal geometry and do not show hypervalent Bi···O interaction. Crystal structures of these compounds show that CFc-Bi bond length is shorter than CPh-Bi bond length due to lower group electronegativity of ferrocenyl vs phenyl and bidentate nature of FcN ligand in ferrocenyl bismuthines.

Conversion Mechanism From Trivalent Bismuth to Bivalent Bismuth Defect Center in Bi-Doped Silica Optical Fiber

We present first-principle methods on the conversion of trivalent bismuth center in Bi-doped silica optical fiber. With the increase of Bi-O distance in different member rings, the reaction energy of transition state configurations gradually become larger. The reaction energy of Bi-6MR is greater than that of Bi-4MR, than that of Bi-5MR, respectively. Based on the basis of the time-dependent density functional theory (TDDFT), transition energy levels of bivalent bismuth defect center models are investigated. Our calculations reveal that the ~1310 nm luminescence of the second optical communication window is likely caused by bivalent bismuth defect center configuration.

Ultrathin Nanotubes of Bi5O7I with a Reduced Band Gap as a High-Performance Photocatalyst.

Bismuth oxyhalide (Bi-O-X) is a group of layered semiconductors, which are promising candidates for photocatalysis due to their inherent internal electric field and adjustable band gap through composition and morphology control. Bismuth-rich Bi-O-X has improved stability and advantageous band structure compared to those of Bi-O-X and hence has attracted an increasing amount of research interest. In this work, ultrathin nanotubes of Bi5O7I with a 5 nm diameter and a 1 nm wall are obtained through a hydrothermal method while the phase and morphology of the products are regulated by the pH values and polyvinylpyrrolidone (PVP) concentration of the reaction system, of which the products can be tuned from BiOI nanosheets to Bi5O7I nanobelts and ultrathin Bi5O7I nanotubes. PVP and pH control is important to the formation of the nanotubes as formation occurs via a PVP-guided oriented attachment from primary nanoparticles of Bi5O7I. The poorly crystalline and porous structure of the resultant bismuth-rich ultrathin nanotubes not only exposes more surface atoms but also exhibits a highly reduced conduction band minimum. The resultant band gap of 2.39 eV (as compared to 3.20 eV for the nanobelts) arises from the undercoordinated bismuth centers brought about by the rich oxygen vacancies in the nanotubes. The largely reduced band gap effectively enhances visible-light absorption, while the short charge-diffusion length of the nanotubes further reduces the charge-carrier loss in recombination.

Synthesis, structure and density functional theory calculations of a novel photoluminescent trisarylborane-bismuth(III) complex.

A novel trisarylborane-Bi(III) complex, tris(4-(dimesitylboryl)phenyl)bismuthine [Bi(PhBMes2 )3 ], in which (Ph=phenyl, and Mes=mesityl), was synthesized via the reaction of bismuth (III) chloride (BiCl3 ) with three equivalents of lithiated (4-bromophenyl)- dimesitylborane [BrPhBMes2 ]. The new trisarylbismuthine was characterized by elemental analysis, ultraviolet-visible (UV-vis) spectroscopy, and NMR (1 H and 13 C) spectroscopy. The molecular structure of Bi(PhBMes2 )3 in the solid state was determined using single-crystal X-ray diffraction analysis, which showed short intermolecular C-H···H-C contact. The complex is a fluorescent emitter (λmax =395nm) at room temperature and a phosphorescent emitter (λmax =423nm) at 77K, which displayed a long lifetime of 495ms. The UV-vis transitions were investigated using density function theory (DFT) and time-dependent (TD)-DFT calculations. Natural bond orbital analysis showed that the bismuth (III) center was mainly Lewis acidic in nature.

Bismuth(III) dication trapped on a chlorobismuthate

Metal cations observed with tetrachloroaluminate anion provide insights into the structure and stability of reactive cations. Addition of tris(3,5-dimethylpyrazolyl)borate anion (TpMe2) to [BiCl2][AlCl4] traps a bismuth(III) dication, [TpMe2Bi]2+, possessing a highly electrophilic bismuth center with short coordinate Bi―N bonds. [TpMe2Bi]2+ has weak interactions with the chlorides of [Bi3Cl13]∞. Strong affinity of [TpMe2Bi]2+ with the triflate (OTf) observed in [TpMe2Bi(OTf)3]- demonstrates the high electrophilicity at bismuth.

Germanium oxide glass based metal-dielectric nanocomposites: fabrication and optical characterization: a review of new developments

We review recent experimental results with germanate glasses containing rare-earth ions (RE) and silver nanoparticles (Ag-NPs) nucleated by appropriate heat-treatment of samples. In one study, the photoluminescence (PL) due to an infrared-to-visible frequency upconversion (UC) process was investigated in Bi2O3–GeO2 (BGO) glasses co-doped with ytterbium (Yb3+) and erbium (Er3+) ions when low concentration of AgNO3 was added to the starting glass composition. By exciting the samples at 980 nm, in resonance with the Yb3+ transition, we investigated the influence of the Ag-NPs on the UC process. The Er3+ PL was enhanced, up to 100%, due to the increased local-field sensed by the RE and to the efficient Yb3+ → Er3+ energy-transfer. In another set of experiments, we studied the behavior of BGO glasses containing thulium ions (Tm3+) and Ag-NPs. The role of energy-transfer from bismuth centers to Tm3+ was investigated. PL and relative gain enhancements of ≈ 56% and 500%, respectively, were observed due to the influence of Ag-NPs. Using a pump laser operating at 808 nm (6 W) and a probe laser at 1470 nm (0.6 mW) the relative gain measured at 1470 nm was 4.5 dB/cm. The results from the two sets of experiments indicate that Yb3+/Er3+ co-doped BGO glass with Ag-NPs is an efficient upconverter and Tm3+ doped BGO glass with Ag-NPs can be used as efficient optical amplifier in the short-wave infrared region.

Problems of development of tunable hybrid bismuth – erbium fibrelasers

Experimental data and experience in the development of tunable fibre lasers based on active bismuth centres in silica glasses with different compositions and luminescence bands in the range 1200–1800 nm are considered. It is shown that continuous-wave narrow-band laser radiation with a milliwatt power (1–10 mW) covering this wavelength range can be obtained using hybrid fibre schemes and, probably, co-doping of matrices with bismuth and erbium. Continuously tunable bismuth fibre lasers with partially overlapping spectral ranges of 1270–1370, 1360–1540, and 1600–1800 nm are studied. Hybrid schemes of fibre lasers emitting in the spectral range from 1500 to 1600 nm, which includes the erbium luminescence band, are proposed.