Benzotriazole Ligands Research Articles

Harnessing benzotriazole as a sustainable ligand in metal-catalyzed coupling reactions.

Coupling reactions play a crucial role in drug development enabling the rapid expansion of structure-activity relationships (SARs) during drug discovery programs to identify a clinical candidate and simplify subsequent drug development processes. In particular, their relevance in clinical medicine and drug discovery has increased significantly in the last two decades. To facilitate these metal-catalyzed coupling reactions, suitably designed ligands are necessary and from the industrial point of view, sustainable and cost-effective ligands are of current need. Benzotriazole, a non-toxic, thermally stable, and inexpensive bidentate ligand, exhibits strong electron donating and electron accepting properties, along with excellent solubility in various organic solvents. It has been extensively explored as a synthetic auxiliary in the past; in recent years, benzotriazole and its derivatives have been used as ligands in metal-catalyzed coupling reactions. The facile construction of carbon-carbon and carbon-heteroatom bonds in the presence of versatile benzotriazole ligands makes it an indispensable ligand for catalytic transformations. The present feature article mainly emphasizes the advances in the utilization of benzotriazole as a ligand in a diverse range of C-C, C-N, C-O, and C-S coupling reactions.

Antifungal activity of Co(II) and Cu(II) complexes containing 1,3-bis(benzotriazol-1-yl)-propan-2-ol on the growth and virulence traits of fluconazole-resistant Candida species: synthesis, DFT calculations, and biological activity

Relevant virulence traits in Candida spp. are associated with dimorphic change and biofilm formation, which became an important target to reduce antifungal resistance. In this work, Co(II) complexes containing a benzotriazole derivative ligand showed a promising capacity of reducing these virulence traits. These complexes exhibited higher antifungal activities than the free ligands against all the Candida albicans and non-albicans strains tested, where compounds 2 and 4 showed minimum inhibitory concentration values between 15.62 and 125 μg mL−1. Moreover, four complexes (2–5) of Co(II) and Cu(II) with benzotriazole ligand were synthesized. These compounds were obtained as air-stable solids and characterized by melting point, thermogravimetric analysis, infrared, Raman and ultraviolet/visible spectroscopy. The analysis of the characterization data allowed us to identify that all the complexes had 1:1 (M:L) stoichiometries. Additionally, Density Functional Theory calculations were carried out for 2 and 3 to propose a probable geometry of both compounds. The conformer Da of 2 was the most stable conformer according to the Energy Decomposition Analysis; while the conformers of 3 have a fluxional behavior in this analysis that did not allow us to determine the most probable conformer. These results provide an important platform for the design of new compounds with antifungal activities and the capacity to attack other target of relevance to reduce antimicrobial resistance.

Synthesis of benzotriazole functionalized ZIF-8 by postsynthetic modification for enhanced CH4 and CO2 uptakes

In this work, a series of functionalized ZIF-8 were synthesized via incorporation of benzotriazole ligands into the framework with a post-synthetic method. The crystal structure and porosity were preserved for all functionalized samples. Although a relatively low percentage of ligand exchange (approximately 10–22%) was observed due to steric and kinetic effects, a remarkable improvement was found in CO2 and CH4 uptake capacities due to the incorporation of more polar N sites into the structure and the change in pore size of the frameworks. The resulting ZIF-8-S5 exhibited 45.17(CO2) and 15.08 (CH4) cm3 g−1 at 273 K under 1.2 bar, which corresponds to an enhancement of 20 and 35% compared to pristine ZIF-8. Further, all functionalized samples showed the significant improvement of selective CO2 over N2.

Structural and Electronic Control of the Bidentate 1-(2-pyridyl)benzotriazole Ligand in Copper Chemistry with Application to Catalysis in the A3 Coupling Reaction.

The hybrid bidentate 1-(2-pyridyl)benzotriazole (pyb) ligand was introduced into 3d transition metal catalysis. Specifically, [CuII (OTf)2 (pyb)2 ]⋅2 CH3 CN (1) enables the synthesis of a wide range of propargylamines by the A3 coupling reaction at room temperature in the absence of additives. Experimental and high-level theoretical calculations suggest that the bridging N atom of the ligand imposes exclusive trans coordination at Cu and allows ligand rotation, while the N atom of the pyridine group modulates charge distribution and flux, and thus orchestrates structural and electronic precatalyst control permitting alkyne binding with simultaneous activation of the C-H bond via a transient CuI species.

(para‐Cymene)Ru(II) Complexes with Chelating Benzotriazole Ligands: Application in Oxidation and Reduction Catalysis

Abstract1‐Heteroaryl‐substituted benzotriazole motifs represent a new class of bidentate chelating ligands for several transition metals. Although metal complexes having such ligands in tris‐ and bis‐chelated binding have been extensively studied, investigation of mono‐chelated metal complexes, especially their structural and catalytic properties, is rarely explored. In this work, two such complexes – [(para‐cymene)Ru(BTZ‐2P)Cl]PF6 and [(para‐cymene)Ru(BTZ‐2Q)Cl]PF6, (BTZ‐2P=1‐(pyridine‐2‐yl)‐1H‐benzo[d][1,2,3]triazole; BTZ‐2Q=1‐(quinoline‐2‐yl)‐1H‐benzo[d][1,2,3]triazole) have been synthesized and characterized through various spectroscopic method and X‐ray crystallography. Their electronic spectra and electrochemical properties have also been explored. Both the complexes have been successfully applied in two types of important catalytic processes – (a) oxidation of aryl olefins to corresponding aromatic carbonyl compounds, and (b) transfer hydrogenation of aromatic carbonyl compounds to the corresponding alcohols.

Novel alcohol vapour sensor based on the mixed-ligand modified MOF-199 coated quartz crystal microbalance

ABSTRACT Alcohol vapour sensors can be used in many fields, such as food quality monitoring, etc. Herein, we developed an alcohol vapour sensor based on the quartz crystal microbalance (QCM) technology. A modified metal-organic frameworks (MOFs), m-MOF-199 was coated on the QCM electrode surface. The different coating methods, including drop coating, spin coating and electrospray were used for preparing a thin film on the surface of the QCM electrode. MOF-199 was modified by mixed-ligand strategy in which benzotriazole ligand was introduced into the structure of MOF-199 and characterised by FT-IR, XRD, BET and FE-SEM techniques. The smaller dimension of m-MOF199 led to a better thin film and enhanced QCM sensor efficiency. In order to evaluate the QCM sensor, ethanol was used as a model compound. The developed ethanol sensor showed two linear ranges in the concentration between of 0.5–30 mg L−1 and 30–300 mg L−1 with a 0.1 and 0.5 mg L−1, LOD and LOQ, respectively. The relative standard deviation (RSD %) of measurements was less than 10%. The developed sensor could be applied for various applications including food, environmental and bioanalysis.

Long-term entrapment and temperature-controlled-release of SF6 gas in metal-organic frameworks (MOFs).

In this work, a metal–organic framework (MOF), namely MFU-4, which is comprised of zinc cations and benzotriazolate ligands, was used to entrap SF6 gas molecules inside its pores, and thus a new scheme for long-term leakproof storage of dangerous gasses is demonstrated. The SF6 gas was introduced into the pores at an elevated gas pressure and temperature. Upon cooling down and release of the gas pressure, we discovered that the gas was well-trapped inside the pores and did not leak out – not even after two months of exposure to air at room temperature. The material was thoroughly analyzed before and after the loading as well as after given periods of time (1, 3, 7, 14 or 60 days) after the loading. The studies included powder X-ray diffraction measurements, thermogravimetric analysis, Fourier-transform infrared spectroscopy, scanning electron microscopy, 19F nuclear magnetic resonance spectroscopy and computational simulations. In addition, the possibility to release the gas guest by applying elevated temperature, vacuum and acid-induced framework decomposition was also investigated. The controlled gas release using elevated temperature has the additional benefit that the host MOF can be reused for further gas capture cycles.

An inorganic–organic hybrid constructed from Keggin polyoxoanions and benzotriazole ligands modulated by two dinuclear silver(I) clusters

A new polyoxometalate (POM)-based inorganic–organic hybrid, [Ag4(SiMo12O40)(HBTA)8]·8H2O (1), constructed from the Keggin-type polyoxomolybdates and benzotriazole (HBTA) ligands linked by two dinuclear silver(I) clusters has been obtained and characterized by single-crystal X-ray diffraction and IR spectrum. In 1, a pair of parallel Ag2(HBTA)4 units fixed to the central [SiMo12O40]4− stick out like a barbell to support the whole structure. These clusters are extended into the wave-like layers by the strong π–π stacking interactions and hydrogen bonds. The 2D layers are further extended into a 3D supramolecular structure by means of hydrogen bonds (C4–H4⋯O10) between the nitrogen atoms of the HBTA ligands and the oxygen atoms of [SiMo12O40]4− anions. Luminescence property of 1 in CH3CN solution has been investigated. In addition, 1-CPE possesses good electrocatalytic activity toward the reduction of KNO2, H2O2 and KBrO3.

Thermal, spectral, DFT and biological activity evaluation of Co(II), Ni(II) and Cu(II) complexes of N,S-chelated benzotriazole ligand

[ML2]·yC2H5OH·zH2O complexes (M=CoII (1) and NiII (2), y = 4, z = 0; M=CuII (3), y = 0, z = 3; HL = N-(2-thiazolyl)-1H-benzotriazole-1-carbothioamide) were prepared, characterized (elemental analysis, TG, FT IR, UV–Vis, EPR, magnetic and conductance measurement) and tested for their antimicrobial activity against Escherichia coli and Staphylococcus aureus. Complexes 1–3 consist of a metal center having a considerable tetrahedral distortion in the xy-plane from the square planar stereochemistry MN2S2 formed by the two deprotonated benzotriazole ligands. TD-DFT calculations were carried out at B3LYP/6-31G* level of theory to understand the electronic structure and to explain the related experimental findings. Natural bond orbital analysis was performed to provide details about the electronic arrangement, type of hybridization and the nature of bonding. Coordination of HL to CoII gave rise to inactive compound, but the development of NiII and CuII complexes did not clearly change the toxicity of the free HL.

Titanium complexes containing bidentate benzotriazole ligands as catalysts for the ring opening polymerization of lactide

The selective syntheses of titanium complexes containing the 2-(2H-benzo[d][1,2,3]triazol-2-yl)-4,6-di-tert-pentylphenol (LH) ligand, namely [LTiCl2(μ-Cl)]2 (1), LTiCl3(THF) (2), L2Ti(NMe2)2 (3), L2TiCl2 (4) and L2Ti(O-i-Pr)2 (5), were achieved by changing the solvents or metal precursors. The solid state structures of 1–5 were revealed by single-crystal X-ray analyses. Complexes 2 and 5 showed a fast thermal exchange process of the benzotriazole ligand L. Among 1–5, complex 5 was proven as a highly effective catalyst for the controlled ring opening polymerization (ROP) of lactide (LA), as shown by the linearity of the molecular weight versus [LA]/[Ti] ratio as well as very narrow PDI values of the PLA polymers obtained.

Bis(1H-benzimidazole-κN3)bis[2-(naphthalen-1-yl)acetato-κ2O,O′]nickel(II) monohydrate

In the title compound, [Ni(C12H9O2)2(C7H6N2)2]·H2O, The NiII cation is located on a twofold rotation axis and is six-coordinated in a distorted NiN2O4 octa­hedral geometry. The asymmetric unit consists of a nickel(II) ion, one 2-(naphthalen-1-yl)acetate anion, a neutral benzotriazole ligand and one half of a lattice water mol­ecule. The crystal packing is stabilized by O—H⋯O and N—H⋯O hydrogen bonds. The title compound is isotypic with its CdII analogue.

Solvothermal synthesis, crystal structures and photoluminescence properties of the novel Cd/X/α,ω-bis(benzotriazole)alkane hybrid family (X = Cl, Br and I)

Seven organic-inorganic hybrid solids, namely, [(CdI2)2(L1)2] (1), [(CdBr2)3(L1)2]n (2), [(CdCl2)5(L1)2]n (3), [(CdI2)(L2)]n (4), [(CdBr2)(L3)]n (5), [(CdBr2)2(L4)2]n (6), and [(CdI2)4(L4)4]n (7), have been obtained via the self-assembly of CdX2 (X = Cl, Br or I) with the four structurally related flexible organic ligands 1,2-bis(benzotriazole)ethane (L1), 1,3-bis(benzotriazole)propane (L2), 1,4-bis(benzotriazole)butane (L3) and 1,6-bis(benzotriazole)hexane (L4) under solvothermal conditions. Compound 1 presents a binuclear structure with a [Cd2N12C4] 18-membered cycle. In 2, the L1 ligands locate alternately on the two sides of the 1-D inorganic chain formed by papilionaceous [Cd2Br2] subunits. The 1-D hexagonal [CdCl2]n grid inorganic chains in 3 are generated by vertex-loss cubane-like [Cd3Cl4] motifs through sharing faces, which are further connected by L1 ligands to give a 2-D hybrid layer. For compound 4, the L2 ligands and 4-connected Cd centres link each other to give a 1-D single chain. In 5 and 6, [Cd2Br4] units are connected by L3 and L4 to generate a 2-D (4, 4) net and 1-D double chain structure, respectively. Four independent [CdI2] centres and four L4 ligands in 7 generate an extraordinarily large [Cd4N24C24] 52-membered cycle. The varying structures of 1–7 indicate that the spacer length of the bis(benzotriazole)alkane ligands and counter-anions play an essential role in the formation of the framework of the Cd(II) hybrid materials. Strong π–π stacking interactions between the benzotriazole ligands pack these low-dimensional hybrid chains or layers into high-dimensional supramolecular frameworks. The UV-vis diffuse reflectance spectra and solid state luminescence measurements show that compounds 1–7 are potential semiconductor and photoluminescence materials.

Syntheses and Magnetostructural Investigations on Kuratowski-Type Homo- and Heteropentanuclear Coordination Compounds [MZn4Cl4(L)6] (MII= Zn, Fe, Co, Ni, or Cu; L = 5,6-Dimethyl-1,2,3-benzotriazolate) Represented by the NonplanarK3,3Graph

Homo- and heteropentanuclear coordination compounds [MZn(4)Cl(4)(L)(6)] (M(II) = Zn, Fe, Co, Ni, or Cu; L = 5,6-dimethyl-1,2,3-benzotriazolate) were prepared containing mu(3)-bridging N-donor ligands (1,2,3-benzotriazolate), which are structurally related to the fundamental secondary building unit of Metal-organic Framework Ulm University-4 (MFU-4). The unique topology of these T(d)-symmetrical compounds is characterized by the nonplanar K(3,3) graph, introduced into graph theory by the mathematician Casimir Kuratowski in 1930. The following "Kuratowski-type" compounds were investigated by single-crystal X-ray structure analysis: [MZn(4)Cl(4)(Me(2)bta)(6)].2DMF (M(II) = Zn, Fe, Co, and Cu; DMF = N,N'-dimethylformamide) and [MZn(4)Cl(4)(Me(2)bta)(6)].2C(6)H(5)Br (M(II) = Co and Ni; C(6)H(5)Br = bromobenzene). The mu(3)-bridging benzotriazolate ligands span the edges of an imaginary tetrahedron, in the center of which a redox-active octahedrally coordinated M(II) ion is placed. Four Zn(II) ions are located at the corners of the coordination units. Each Zn center is bound to a monodentate Cl(-) anion and three N-donor atoms stemming from different benzotriazolate ligands. The fact that open-shell redox-active M(II) ions can be introduced selectively into the central octahedral coordination sites is unambiguously proven by a combination of magnetic measurements, UV-vis spectroscopy, and energy-dispersive X-ray and inductively coupled plasma atomic emission spectrometry analysis. The phase purity of all compounds was checked by powder X-ray diffractometry, IR spectroscopy, and elemental analysis. The electronic spectra and magnetic properties of the compounds are in complete agreement with their structures determined from single-crystal data. Thermogravimetric analysis shows that all compounds possess a high thermal stability up to 673 K. The pentanuclear compounds retain their structural integrity in solution, as evidenced by time-of-flight mass spectrometry analysis and comparative solution and solid-state diffuse-reflectance spectroscopy. High stability paired with the presence of redox-active metal ions and Lewis-acidic Zn centers renders Kuratowski-type compounds structural and functional models for future MFU-4-type bi- and multifunctional heterogeneous catalysts.

Two anionic [Cu I6X7] nn− ( X=Br and I) chain-based organic–inorganic hybrid solids with N-substituted benzotriazole ligands

Solvothermal reactions of the flexible ligand 1,6-Bi(benzotriazole)hexane with CuI and KI or CuBr and KBr in ethanol generate two hybrid compounds, namely, {(HETA)[(Cu 6I 7)(ETA) 2]} n ( 1) and {K(Cu 6Br 7)(BBTH)} n ( 2) (ETA= N-ethylbenzotriazole, HETA=protonated N-ethylbenzotriazole, BBTH=1,6-bi(benzotriazole)hexane). In 1, two [Cu 3I 4] vertex missing cubane-like subunits link each other by sharing one I atom to give a [Cu 6I 7] cluster, which further form novel 1D [Cu 6I 7] n n− anionic chain. Two in-situ generated ETA ligands finished the 4-coordinated environments of copper centers and another one discrete protonated ETA ligand keeps the charge neutrality for 1. In complex 2, bowl-shaped [Cu 5Br 4] clusters and rhomboid [Cu 2Br 2] dimers link each other to generate a [Cu 6Br 7] n n− 1D chain. BBTH ligands complete the tetrahedral spheres of Cu(I), and 7-coordinated K atoms further extend the 1D chain motifs to a 2D hybrid layer of 2. The UV–vis diffuse reflectance spectrum and luminescence measurements show that compound 1 and 2 both are potential semiconductor and photoluminescence materials.

Zinc and cadmium complexes of pyridyl-benzotriazole: Syntheses, structures and supramolecular interaction

Five novel complexes with two pyridine substituted benzotriazole ligands, 1-(2-pyridyl)benzotriazole (L1) and 1-(4-pyridyl)benzotriazole (L2), [Zn(L1) 2Cl 2] ( 1), [{Zn(L1) 2Cl 2}·(L1) 2] ( 2), [Zn(L2) 2Cl 2] ( 3), [{Zn(L2)(H 2O) 3( μ 2-SO 4)}·H 2O] ( 4), and [{Cd(L2)(H 2O) 3( μ 2-SO 4)}·H 2O] ( 5) were synthesized. The details of the structures were characterized by X-ray single crystal analysis, revealing that these complexes were assembled together via supramolecular interaction, such as, hydrogen bonding and π– π interactions. The influence of organic ligands, anions and reaction conditions in the formation of the complexes were investigated.

The Benzotriazolate Coordination Polymer $^1_\infty$[Eu(Btz)2(BtzH)2], Containing Divalent Europium

AbstractThe reaction of europium metal with a melt of the amine 1H‐1,2,3‐benzotriazole yields single crystalline yellow $^1_\infty$[Eu(Btz)2(BtzH)2], Btz– = 1,2,3‐benzotriazolate anion, C6H4N3–, BtzH = 1H‐1,2,3‐benzotriazole, C6H5N3, and H2 gas. No additional solvent was used. The new compound adopts a strand‐like structure and exhibits a square anti‐prismatic coordination of europium by nitrogen atoms. As europium is divalent, this is the first example of a divalent rare earth benzotriazolate. Both benzotriazolate and benzotriazole ligands function as μ‐η1:η1 linkers between different europium atoms, their third nitrogen atom being involved in intra‐strand hydrogen bridges. Although the structure of each strand can be refined in a smaller subcell, the arrangement of strands to one another necessitates a refinement in a larger supercell.

Supramolecular networks with 1-substituted benzotriazole ligands and transition metals

1-(2-Pyridyl)benzotriazole (L1) and 1-(4-pyridyl)benzotriazole (L2) with transition metal cations Co(II), Ni(II) and Cu(II) give four coordination complexes, [{Cu(L1)2(H2O)2} · 2NO3] (1), [{Co(L1)2(H2O)2} · 2NO3] (2), [Ni(L2)2(NO3)2(H2O)2] (3), and [Cu2(L2)2(CH3COO)4] (4). In 1–4, different supramolecular frameworks are formed through hydrogen bonding and/or π–π interactions.

Investigation of the zinc(II) acetylacetonate/benzotriazole reaction system in the presence of bridging N, N′-ligands: Pentanuclear, enneanuclear and polymeric complexes

The reaction of Zn(acac) 2 with btaH (1,2,3-benzotriazole) in dmf yielded the pentanuclear complex [Zn 5(bta) 6(acac) 4(dmf)]·dmf ( 1·dmf). In the presence of pyrazine, the pentanuclear [Zn 5(bta) 6(acac) 4(dmf)]·3.7dmf ( 2·3.7dmf) and enneanuclear [Zn 9(bta) 12(acac) 6]·6dmf ( 3·6dmf) complexes were formed, whereas in the presence of 4,4′-bpy the 1D coordination polymer [Zn(acac) 2(4,4′-bpy)] n ( 4) was isolated. The molecular structures of 1·dmf and 2·3.7dmf reveal that the [Zn 5] clusters consist of four Zn II ions which span the corners of a tetrahedron and the fifth resides at its centre. The molecular structure of 3·6dmf reveals that the [Zn 9] clusters consist of two corner sharing tetrahedra and the structure can be described as the addition of two [Zn 5] clusters of 1·dmf and/or 2·3.7dmf followed by the simultaneous abstraction of [Zn(acac) 2] and dmf molecules; this alternative was accomplished by recrystallization of 1·dmf from dmf which yielded 3·6dmf. Each of the μ 3-κ N:κN′:κN′′ benzotriazolate ligands in 1·dmf, 2·3.7dmf and 3·6dmf spans an edge of the tetrahedron. The molecular structure of 4 reveals mononuclear [Zn(acac) 2] units bridged via 4,4′-bpy molecules to 1D coordination polymer. Characteristic IR bands of the four complexes are discussed in terms of the coordination modes of the ligands and known structures.

Catena-Poly[dipropylammonium [[bis(benzotriazolato-κN1)zinc(II)]-μ-benzotriazolato-κ2N1:N3

In the title compound, {(C6H16N)[Zn(C6H4N3)3]}n, the ZnII atom has a distorted tetra­hedral geometry defined by four N atoms from four benzotriazolate (BTA) ligands. The compound is composed of extended polymeric chains in which two BTA N atoms bridge [Zn(BTA)2] fragments along [001]. Cations and anions are linked by N—H⋯N hydrogen-bond inter­actions along [010].

Nonanuclear Coordination Compounds Featuring {M9L12}6+ Cores (M = NiII, CoII, or ZnII; L = 1,2,3‐Benzotriazolate)

AbstractSyntheses, characterization, and magnetic properties of three nonanuclear coordination compounds with the molecular formulae [Ni9(bta)12(NO3)6(MeOH)6]·4THF (1) (btaH = 1,2,3‐benzotriazole; THF = tetrahydrofuran), [Co9(bta)12(MeOH)18][(NO3)6]·9C6H6 (C6H6 = benzene) (2), and [Zn9(Me2bta)12(CH3COO)6]·3DMF (Me2btaH = 5,6‐dimethyl‐1,2,3‐benzotriazole; DMF = N,N′‐dimethylformamide) (3) are presented. The solid‐state structures of all the compounds were determined by single‐crystal X‐ray structure analysis revealing the presence of structurally similar {M9L12}6+ cores (M = NiII, CoII, or ZnII; L = 1,2,3‐benzotriazolate) in which the metal centers are bridged by μ3‐benzotriazolates. The charges of the cationic {M9L12}6+ moieties in 1 and 3 are balanced by six nitrate and acetate anions coordinated to the peripheral metal atoms, respectively, whereas 2 is a cationic metal complex with six noncoordinated nitrate counterions in the crystal lattice. All the metal centers in each compound are hexacoordinate, except for the peripheral metal centers in 3 which are pentacoordinate. The nonanuclear cores can be formally subdivided into two metallosupramolecular tetrahedra which bear five metal ions each, and share a common apex. All compounds have been prepared by using excess of ligand, which acts as an auxiliary base, serving to abstract protons from the coordinated benzotriazole ligand. Magnetic susceptibility studies (2–290 K) show net antiferromagnetic intramolecular coupling for 2, while 1 displays both ferro‐ and antiferromagnetic coupling contributions. Both compounds exhibit strong ligand field effects in their magnetic properties. Phase purity of the compounds was ascertained by X‐ray powder diffraction (XRPD) analysis, IR spectroscopy, and elemental analysis.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)