Terpy Ligand Research Articles

Constructing Alkyl Chain Modified FeII Spin Crossover Complexes through Complementary Pair Strategy

AbstractFour alkyl chains and cyclohexane modified FeII complexes [Fe(Ln)(L’)](ClO4)2⋅solv (n=1, 2, 3, 4) were synthesized and characterized. X‐ray diffraction study showed that these complexes were constituted by asymmetric mononuclear FeII entities, incorporating alkyl‐chain‐modified bppCOOH (2,6‐bis(1H‐pyrazol‐1‐yl)isonicotinic acid) ligands and 6,6’’‐2,6‐dimethoxyphenyl‐substituted terpy ligand (L’). Magnetic susceptibility measurements revealed that complexes 1, 2, and 3 were in the high spin state across the measured temperature range, whereas complex 4 displayed an incomplete spin crossover phenomenon, with a transition temperature (T1/2) at 240 K. Investigations into variable‐temperature structure and magneto‐structural correlations revealed that the integration of alkyl‐chain‐modified bipyridyl units fostered the π⋅⋅⋅π intra‐ and intermolecular interactions, contributing to distinct crystal stacking and spatial configurations in complex 4 when compared to its counterparts. These findings underscore the pivotal influence of intramolecular interactions on the FeII spin states and highlight the significance of designing flexible ligands for modulating spin‐crossover characteristics.

Heterometallic bridged Pt(II)‐Zn(II) complexes: Influence of the substituent in 4′‐position in inert terpy ligand on antigenotoxicity, potential antitumor activity and mechanism of interactions of the complexes with biomolecules

The synthesis and characterization of novel hetrometallic complexes [{cis‐PtCl(NH3)2(μ‐4,4′‐bipyridyl)ZnCl(terpy‐Cl)}](ClO4)2 (C1a), [{trans‐PtCl(NH3)2(μ‐4,4′‐bipyridyl)ZnCl(terpy)}](ClO4)2 (C2a), [{cis‐PtCl(NH3)2(μ‐pyrazine)ZnCl(terpy‐Cl)}](ClO4)2 (C3a) and [{trans‐PtCl(NH3)2(μ‐pyrazine)ZnCl(terpy‐Cl)}](ClO4)2 (C4a) (where terpy‐Cl = 4′‐chloro‐2,2′:6′,2′′‐terpyridine) was done. Acid–base titrations were performed by UV–Vis spectrophotometric method to evaluate the pKa values of corresponding aqua complexes. Interactions between complexes and important biomolecules, guanosine‐5′‐monophosphate (5′‐GMP) and glutathione (GSH) were examined by 1H NMR spectroscopy. The chloride substituent at the 4′ position on the middle pyridine ring of terpyridine ligand significantly affects the coordination of biomolecules, as well as overall stability of complexes. The complexes were evaluated in vitro for the antioxidant prevention of DNA damages. All tested novel complexes demonstrated a significant reduction in DNA damage against oxidative modifications of DNA caused by the hydroxyl and peroxyl radicals. Also, cytotoxicity evaluation showed that significant cytotoxicity occurs only after long‐term effect of C1a, C2a and C3a, complexes in HCT‐116 cells. Molecular docking studies predict results in agreement with experimental research.

Sterically attenuated electronic communication in cobalt complexes of meridional isoquinoline-derived ligands for applications in electrocatalysis.

The ability to synthetically tune the ligand frameworks of redox-active molecules is of critical importance to the economy of solar fuels because manipulating their redox properties can afford control over the operating potentials of sustained electrocatalytic or photoelectrocatalytic processes. The electronic and steric properties of 2,2':6',2″-terpyridine (Terpy) ligand frameworks can be tuned by functional group substitution on ligand backbones, and these correlate strongly to their Hammett parameters. The synthesis of a new series of tridentate meridional ligands of 2,4,6-trisubstituted pyridines that engineers the ability to finely tune the redox potentials of cobalt complexes to more positive potentials than that of their Terpy analogs is achieved by aryl-functionalizing at the four-position and by including isoquinoline at the two- and six-positions of pyridine (Aryl-DiQ). Their cobalt complex syntheses, their electronic properties, and their catalytic activity for carbon dioxide (CO2) reduction are reported and compared to their Terpy analogs. The cobalt derivatives generally experience a positive shift in their redox features relative to the Terpy-based analogs, covering a complementary potential range. Although those evaluated fail to produce any quantifiable products for the reduction of CO2 and suffer from long-term instability, these results suggest possible alternate strategies for stabilizing these compounds during catalysis. We speculate that lower equilibrium association constants to the cobalt center are intrinsic to these ligands, which originate from a steric interaction between protons on the pyridine and isoquinoline moieties. Nevertheless, the new Aryl-DiQ ligand framework has been engineered to selectively tune homoleptic cobalt complexes' redox potentials.

Hysteretic Spin Crossover with High Transition Temperatures in Two Cobalt(II) Complexes.

Cooperative spin crossover transitions with thermal hysteresis loops are rarely observed in cobalt(II) complexes. Herein, two new mononuclear cobalt(II) complexes with hysteretic spin crossover at relatively high temperatures (from 320 to 400 K), namely, [Co(terpy-CH2OH)2]·X2 (terpy-CH2OH = 4'-(hydroxymethyl)-2,2';6',2″-terpyridine, X = SCN-(1) and SeCN- (2)), have been synthesized and characterized structurally and magnetically. Both compounds are mononuclear CoII complexes with two chelating terpy-CH2OH ligands. Magnetic measurements revealed the existence of the hysteretic SCO transitions for both complexes. For compound 1, a one-step transition with T1/2↑= 334.5 K was observed upon heating, while a two-step transition is observed upon cooling with T1/2↓(1) = 329.3 K and T1/2↓(2) = 324.1 K (at a temperature sweep rate of 5 K/min). As for compound 2, a hysteresis loop with a width of 5 K (T1/2↓ = 391.6 K and T1/2↑ = 396.6 K, at a sweep rate of 5 K/min) can be observed. Thanks to the absence of the crystallized lattice solvents, their single crystals are stable enough at high temperatures for the structure determination at both spin states, which reveals that the hysteretic SCO transitions in both complexes originate from the crystallographic phase transitions involving a thermally induced order-disorder transition of the dangling -CH2OH groups in the ligand. This work shows that the modification of the terpy ligand has an important effect on the magnetic properties of the resulting cobalt(II) complexes.

C–H Metalation of Terpyridine Stereoisomers with Ni(II), Pd(II), and Pt(II)

Ni(II), Pd(II), and Pt(II) complexes [M(Y-terpy)X] (X = Cl or Br) containing the tridentate N^C^N-cyclometalating 2,3′:5′,2″and 2,2′:4′,2″ stereoisomers of the well-known tridentate N^N^N ligand 2,2′:6′,2″-terpyridine (terpy) were synthesised in moderate to good yields through C–H activation. For the Pt complexes, the phenyl ethynide derivatives [Pt(Y-terpy)(C≡CPh)] were also obtained under Sonogashira conditions. In contrast to this, C^N^N cyclometalated complexes using the 2,2′:6′,3″- and 2,2′:6′4″-terpy isomers were not obtained. Comparison of the N^C^N complexes of the cyclometalated 2,3′:5′,2″- and 2,2′:4′,2″-terpy ligands with complexes [M(dpb)Cl] of the prototypical N^C^N cyclometalating ligand dpb− (Hdpb = 2,6-diphenyl-pyridine) showed higher potentials for the terpy complexes for the ligand-centred reductions in line with the superior π-accepting properties of the terpy ligands compared with dpb. Metal-centred oxidations were facilitated by the dpb ligand carrying a central σ-donating phenyl group instead of a metalated pyridine moiety. The same trends were found for the long-wavelength absorptions and the derived electrochemical and optical band gaps. The lower σ-donating capacities of the cyclometalated terpy derivatives is also confirmed by a reduced trans influence in the structure of [Ni(2,3′:5′,2″-terpy)Br0.14/OAc0.86]. Attempts to re-crystallise some poorly soluble Pd(II) and Pt(II) complexes of this series under solvothermal conditions (HOAc) gave two structures with N-protonated cyclometalated pyridine moieties, [Pt(2,3′:5′,2″-terpyH)Cl].Cl and [Pd(2,3′:5′,2″-terpyH)Cl2].

Linkage-specific identification and quantification of sialylated glycans by TIMS-TOF MS through conjugation with metal complexes

Mass spectrometry is an indispensable technology for the characterization of glycans. However, specific identification of isomeric glycans especially sialylated glycan isomers using mass spectrometry alone is challenging, which is why orthogonal techniques are needed. Aiming to achieve simple, rapid, and specific identification of sialyl-linkage isomers, we reported herein a trapped ion mobility spectrometry time of flight mass spectrometry (TIMS-TOF MS) method for linkage-specific identification of sialylated glycans through conjugation with metal complexes. Two pairs of sialyl-linkage isomers including 3'/6′-sialyllactose (3'/6′-SL) and 3'/6′-sialyl-N-acetyllactosamine (3'/6′-SLN) conjugated with the diethylenetriamine (DETA) or 2,2′; 6′,2″-terpyridine (Terpy) ligand and transition metal ion (Mn2+, Fe2+, Co2+, Ni2+, Cu2+, or Zn2+) were studied by TIMS-TOF MS. The two pairs of sialylated isomers were successfully separated with a metal-ligand system, and relative quantification of sialyl-linkage isomers was demonstrated. In addition, the linkage of the sialic acid moiety can also be distinguished with MS/MS in combination with the metal-ligand system.

Synthesis, structure characterization and properties of a new oxidovanadium(IV) coordination polymer incorporating bridging (MoO4)2– and (Mo8O26)4– ligands

Abstract Hydrothermal synthesis, crystal structure and properties of a new heterometallic coordination polymer [(VO(terpy))4(MoO4)2(Mo8O26)]·2H2O (1) (terpy = 2,2′;6′,2″-terpyridine) are reported. Compound 1 contains two crystallographically unique vanadium(IV) atoms, bonded to a terminal oxido ligand and further coordinated to a terpy ligand. The three N atoms of terpy occupy the meridional sites of a distorted {VN3O3} octahedron. A γ-octamolybdate (Mo8O26)4– located on an inversion centre and a tetraoxidomolybdate (MoO4)2– function as bridging ligands. The μ3-bridging tridentate binding of (MoO4)2– leads to the formation of a {V4Mo2O12}4+ cationic unit consisting of an eight-membered heterometallic {Mo2V2O4} ring with protruding oxidovanadium handles. A pair of {V4Mo2O12}4+ units are bridged by the centrosymmetric (Mo8O26)4– ligand, resulting in the formation of an infinite chain of alternating {V4Mo2O12}4+ cations and (Mo8O26)4– anions.

Dissecting conjugation and electronic effects on the linear and non-linear optical properties of rhenium(I) carbonyl complexes.

Herein, we report a theoretical and experimental analysis of the conjugation and electronic effects on the one-photon (1PA) and two-photon absorption (2PA) properties of a series of Re(I) carbonyl complexes with terpyridine-based ligands. An excellent agreement was obtained between the calculated and experimental 2PA spectra of the κ2N-terpyridine tricarbonyl complexes (1a-b), with 2PA cross sections reaching up to ca. 40 GM in DMF. By stepwise lowering the conjugation length in the terpy ligand and changing the local symmetry around the metal centre, we show that conjugation and delocalisation play a major role in increasing 2PA cross sections, and that the character of the excited states does not directly enhance the non-linear properties of these complexes-contrary to the results observed in 1PA. Altogether, these results give valuable guidelines towards more efficient two-photon-absorbing coordination complexes of Re(I), with potential applications in photodynamic therapy and two-photon imaging.

Ru(terpy)-Based Conducting Polymer in Electrochemical Biosensing of Epinephrine

A heteroleptic [Ru(terpy)2]2+ (terpy = 2,2′:6′,2″-terpyridine) complex was electrochemically polymerized to give the corresponding metal-containing conducting polymer on gold and glassy carbon electrodes. The polymerization of the Ru(II) complex was allowed by a terthiophene functionalization on one of the two terpy coordinating fragments, whereas the presence of -COOH substituents on the second terpy ligand enabled the film to immobilize a tyrosinase enzyme by cross-linking with glutaraldehyde. Then, the Ru(terpy) conducting polymer worked as a transducer as well as an immobilizing agent in the design of amperometric biosensors for the determination of epinephrine. The electrochemical behavior of enzymatic sensors containing Ru(terpy)-based conducting polymers was investigated by differential pulse voltammetry and chronoamperometry. Analytical performances and kinetic parameters were calculated, suggesting a potential application of the reported biosensors in the determination of epinephrine in pharmaceutical products.

Influence of Ligand Denticity and Flexibility on the Molecular Copper Mediated Oxygen Reduction Reaction.

To date, the copper complex with the tris(2-pyridylmethyl)amine (tmpa) ligand (Cu-tmpa) catalyzes the ORR with the highest reported turnover frequency (TOF) for any molecular copper catalyst. To gain insight into the importance of the tetradentate nature and high flexibility of the tmpa ligand for efficient four-electron ORR catalysis, the redox and electrocatalytic ORR behavior of the copper complexes of 2,2′:6′,2″-terpyridine (terpy) and bis(2-pyridylmethyl)amine (bmpa) (Cu-terpy and Cu-bmpa, respectively) were investigated in the present study. With a combination of cyclic voltammetry and rotating ring disk electrode measurements, we demonstrate that the presence of the terpy and bmpa ligands results in a decrease in catalytic ORR activity and an increase in Faradaic efficiency for H2O2 production. The lower catalytic activity is shown to be the result of a stabilization of the CuI state of the complex compared to the earlier reported Cu-tmpa catalyst. This stabilization is most likely caused by the lower electron donating character of the tridentate terpy and bmpa ligands compared to the tetradentate tmpa ligand. The Laviron plots of the redox behavior of Cu-terpy and Cu-bmpa indicated that the formation of the ORR active catalyst involves relatively slow electron transfer kinetics which is caused by the inability of Cu-terpy and Cu-bmpa to form the preferred tetrahedral coordination geometry for a CuI complex easily. Our study illustrates that both the tetradentate nature of the tmpa ligand and the ability of Cu-tmpa to form the preferred tetrahedral coordination geometry for a CuI complex are of utmost importance for ORR catalysis with very high catalytic rates.

Mn(terpy)Sb2S4]n, a 1D Network of MnSb4S5 Rings Exhibiting a Pronounced Magnetocaloric Effect and Luminescence

The solvothermal reaction of an aqueous solution of Na3SbS3 or Schlippe's Salt (Na3SbS4·9H2O) in the presence of Mn(ClO4)2·6H2O and terpy (terpy = 2,2':6',2''‐terpyridine) or the [Mn(terpy)]2+ complex led to crystallization of the new compound [Mn(terpy)Sb2S4]n (I). The unique crystal structure of I features chains formed by fused MnSb4S5 rings. The Mn2+ cation is coordinated by one terpy ligand and two S2– anions resulting in a distorted MnN3S2 trigonal bipyramid. The terpy ligands point to the exterior of the chains, distances between neighbored ligands indicate π···π stacking. Magnetic investigations show paramagnetic behavior (µeff = 5.92 µB/Mn2+ at room temperature). Field‐dependent magnetic susceptibility measurements at different temperatures evidence a significant magnetocaloric effect of –ΔS = 20.54 J kg–1 K–1 at T = 2 K for a magnetic field change of ΔB = 9 T. The compound exhibits blue luminescence, and a detailed analysis allowed assignment of the emission and excitation bands to the different constituents of the compound.

Self-assembly of Cu(I) metallomacrocycle and coordination polymers with 2,2′:5′,4″-terpyridine directed by anions and solvents

The reaction of [Cu(MeCN)4]X (X = BF4, PF6) with 2,2′:5′,4″-terpyridine (2,2′:5′,4″-terpy) in MeOH/MeCN under Ar/C2H4 afforded 1-D Cu(I) coordination polymers {[Cu(2,2′:5′,4″-terpy)(MeCN)]BF4}n (1) and {{[Cu(2,2′:5′,4″-terpy)(MeCN)]PF6}2·H2O}n (2). In complex 1, the tetrahedral Cu(I) atoms are bridged by 2,2′:5′,4″-terpy in the head-to-tail fashion to form an infinite 1-D zigzag chain structure. In complex 2, there are two independent infinite 1-D zigzag chain structures along the b- and c-axises in the unit cell. The weak intermolecular π⋯π stacking interactions exist between opposite 2,2′:5′,4″-terpy ligands. The PF6– anions are surrounded by four opposite MeCN molecules in two crossed zigzag chains. In contrast, the reaction of [Cu(MeCN)4]PF6 with 2,2′:5′,4″-terpy in Me2CO/MeCN under Ar/C2H4 afforded Cu(I) metallomacrocycle [Cu4(2,2′:5′,4″-terpy)4](PF6)4·5Me2CO (3). Four Cu(I) atoms are bridged by the four 2,2′:5′,4″-terpy in a head-to-tail fashion to afford a rhombic Cu(I) metallomacrocycle. One distorted Me2CO molecule is encapsulated in the central vacant space of [Cu4(2,2′:5′,4″-terpy)4]4+ core and two PF6– anions are sandwiched between the rhombic Cu(I) metallomacrocyclic layers. The reactions of Cu(NO3)2·3H2O and Cu turnings with 2,2′:5′,4″-terpy in MeOH/MeCN under Ar afforded 1-D Cu(I) coordination polymer {[Cu(2,2′:5′,4″-terpy)(MeCN)]NO3}n (4). It has been proved that complex 4 could be induced by the autoreduction of Cu(II) species to Cu(I) species.

P(v) dications: carbon-based Lewis acid initiators for hydrodefluorination.

The P(iii) dication [(terpy)PPh]2+ is oxidized by reaction with o-chloranil or 9,10-phenanthrenequinone to give the P(v) dications [(terpy)(C6Cl4O2)PPh]2+ and [(terpy)(C14H8O2)PPh]2+, respectively. These species are coordinatively saturated at phosphorus and yet display the ability to effect Lewis acid initiation of hydrodefluorination of fluoroalkanes. Experimental and computational data support the notion that the P(v) dications are Lewis acidic at the para-carbon of the central ring of the terpy ligand.

Synthesis of Camphor-Derived Bis(pyrazolylpyridine) Rhodium(III) Complexes: Structure-Reactivity Relationships and Biological Activity.

Two novel rhodium(III) complexes, namely, [RhIII(X)Cl3] (X = 2 2,6-bis((4 S,7 R)-7,8,8-trimethyl-4,5,6,7-tetrahydro-1 H-4,7-methanoindazol-3-yl)pyridine or 2,6-bis((4 S,7 R)-1,7,8,8-tetramethyl-4,5,6,7-tetrahydro-1 H-4,7-methanoindazol-3-yl)pyridine), were synthesized from camphor derivatives of a bis(pyrazolylpyridine), tridentate nitrogen-donor chelate system, giving [RhIII(H2L*)Cl3] (1a) and [RhIII(Me2L*)Cl3] (1b). A rhodium(III) terpyridine (terpy) ligand complex, [RhIII(terpy)Cl3] (1c), was also synthesized. By single-crystal X-ray analysis, 1b crystallizes in an orthorhombic P212121 system, with two molecules in the asymmetric unit. Tridentate coordination by the N,N,N-donor localizes the central nitrogen atom close to the rhodium(III) center. Compounds 1a and 1b were reactive toward l-methionine (l-Met), guanosine-5'-monophosphate (5'-GMP), and glutathione (GSH), with an order of reactivity of 5'-GMP > GSH > l-Met. The order of reactivity of the RhIII complexes was: 1b> 1a > 1c. The RhIII complexes showed affinity for calf thymus DNA and bovine serum albumin by UV-vis and emission spectral studies. Furthermore, 1b showed significant in vitro cytotoxicity against human epithelial colorectal carcinoma cells. Since the RhIII complexes have similar coordination modes, stability differences were evaluated by density functional theory (DFT) calculations (B3LYP(CPCM)/LANL2DZp). With (H2L*) and (terpy) as model ligands, DFT calculations suggest that both tridentate ligand systems have similar stability. In addition, molecular docking suggests that all test compounds have affinity for the minor groove of DNA, while 1b and 1c have potential for DNA intercalation.

Luminescent and magnetic properties of mononuclear lanthanide thiocyanates with terpyridine as auxiliary ligand

Novel mononuclear lanthanide thiocyanates with 2,2′;6′,2″-terpyridine (terpy), namely isomorphic complexes [Ln(terpy)2(NCS)3] (Ln = Y, Eu, Tb and Dy) were prepared and studied. The effective luminescence sensitization of the Eu, Tb and Dy ions owing to the terpy ligands was observed and corresponding values of the absolute quantum yields were determined. The influence of structural features of the complexes studied on their luminescent properties was analyzed. Slow magnetic relaxation indicating SMM behavior was found for Dy complex.

New platinum(II) and palladium(II) complexes with substituted terpyridine ligands: synthesis and characterization, cytotoxicity and reactivity towards biomolecules.

A series of palladium(II) (1-3) and platinum(II) chloride complexes (4 and 5) with 2,2':6',2″-terpyridine (terpy) derivatives substituted at the 4' position, was synthesized and fully characterized. Single crystal X-ray diffraction analysis of complexes 2, 3 and 5 showed tridentate coordination of the 4'-substituted terpyridine (terpy) ligands to the metal center. Moreover, in vitro cytotoxic activity of these complexes toward a panel of human cancer cell lines (lung cancer A549, colorectal cancer HCT116, ovarian cancer IGROV-1) and toward normal cell line HDF (dermal fibroblast) was determined by Trypan Blue exclusion assay. Overall, the tested compounds manifested a relevant cytotoxicity for the selected cancer cell lines with complex 4 also showing a modest cytotoxicity on the normal cell lines. To better understand the mode of action of these metal complexes, their reactivity with three model proteins, i.e. hen egg white lysozyme (HEWL), cytochrome c (cyt c) and ribonuclease A (RNase A) were comparatively investigated through ESI-MS analysis. The results highlighted a different behavior between the two series of complexes being platinum compounds more reactive toward RNase and cyt c than palladium compounds. Based on the obtained results, it is proposed that in presence of RNase A and cyt c, the platinum complexes undergo activation through release of labile ligands followed by binding to the protein. In contrast, palladium complexes revealed a far lower reactivity implying the likely occurrence of a different mechanism of action.

Switching from sky blue to deep green fluorescent Zn(II) complexes for OLEDs applications

Three new Zn(II) 4′-aryl substituted 2,2′:6′,2′-terpyridine (terpy) complexes of the type [Zn(Ln)2]NO3 complexes (where, L1 = 4′-(4-methylphenyl)−2,2′:6′,2′-terpyridine, L2 = 4′-(3,4,5-trimethoxyphenyl)−2,2′:6′,2′-terpyridine, and L3 = 4′-(2-thiophenyl)−2,2′:6′,2′-terpyridine) were successfully synthesized and photophysical characterizations were done for OLEDs applications. The UV–visible absorption spectra of the complexes exhibited an intense absorption band in the range of 240–380nm owing to a spin-allowed intraligand (π–π*) charge transition. The addition of an electron-donating aryl substituent into the terpy ligand within the complexes induced a significant red-shift of the spectrum. A solid state photoluminescence (PL) analysis revealed a transition from sky blue to green, while the complexes in the DMSO solution which possessed the most emissions appeared sky to deep blue, respectively. A cyclic voltammetry investigation of the complexes revealed a quasi-reversible reduction where the estimated electrochemical data concurred with theoretical calculations. Moreover, the complexes showed an optical band gap of 3.40–3.51eV and a HOMO level from –6.64 to −6.47eV. In addition, all the complexes depicted an excellent thermal stability. Hence, the presented complexes are promising candidates for blue and green fluorescent OLEDs application as electron transport as well as electroluminescent material.

Heteroleptic Complexes of the Tridentate Pyridine‐2,6‐di‐tetrazolate Ligand

AbstractThe synthesis and spectroscopic characterisation of a series of heteroleptic complexes of the tridentate pyridine‐2,6‐di‐(5‐tetrazolate) (pydtz2−) with Co(II), Ni(II), Cu(II) and Zn(II) and pyridine (Py) and H2O as coligands is reported. Single crystal XRD data reveals the formation of octahedrally configured complexes [Co(pydtz)(H2O)(Py)2], [Co(pydtz)(H2O)2(Py)]⋅2H2O, [Ni(pydtz)(Py)3]⋅2Py, and [Zn(pydtz)(H2O)(Py)2]⋅Py, and a markedly Jahn‐Teller distorted octahedral structure for [Cu(pydtz)(H2O)2(Py)]. Magnetic measurements reveal a S = 3/2 high‐spin configuration for the Co(II) complex [Co(pydtz)(H2O)(Py)2], an S = 1 ground state for the Ni(II) derivative and S = 1/2 Cu(II) ions for [Cu(pydtz)(H2O)2(Py)], the latter is supported by electron‐paramagnetic‐resonance spectroscopy. The crystalline materials are subject to severe corrosion as revealed by powder XRD and DSC‐TG experiments. H2O and pyridine co‐crystallisates and coligands are easily cleaved. At the same time DSC‐TG reveal very high stability of the [M(pydtz)] fragments with exothermic decomposition at T > 300 °C. As a consequence, in pyridine solution in all cases the species [M(pydtz)(Py)3] are observed. Ultraviolet‐visible light absorption spectroscopy reveals a strong ligand field procured by the pydtz2− ligand and electrochemical measurements suggest very strong σ‐donation but only weak π‐accepting abilities of pydtz2− compared to the isostructural terpy (2,2’;6’,2’’‐terpyridine) ligand.

Lanthanide Complexes with 2,3-Dimethoxybenzoic Acid and Terpyridine: Crystal Structures, Thermal Properties, and Antibacterial Activities

The lanthanide coordination complexes Er(2,3-DMOBA)3(terpy)(H2O) (1) and [Nd(2,3-DMOBA)3(terpy)(H2O)]2 (2) (2,3-DMOBA = 2,3-dimethoxybenzoate; terpy = 2,2′:6′,2′′-terpyridine) were synthesized and characterized by IR spectroscopy, powder X-ray diffraction (XRD), single-crystal X-ray diffraction, and thermogravimetric analysis. Complex 1 crystallizes in the triclinic system, space group P1, and the mononuclear subunits form a 1D chain structure along the a axis by hydrogen bonds. Complex 2 crystallizes in the monoclinic system, space group P21/c, and the dinuclear subunits are further linked via the offset face-to-face π···π weak stacking interactions to form a supramolecular 2D layered structure. Thermal analysis showed that the complexes have three decomposition steps. The first step is the loss of coordination water molecules. The neutral terpy ligands and partial 2,3-DMOBA ligands are lost in the second step. The remaining 2,3-DMOBA ligands are lost in the third step. The 3D stacked plots for the FT-IR spectra of the evolved gases are recorded and the gaseous products are identified by the typical IR spectra obtained at different temperatures from the 3D stacked plots. Meanwhile, the results of the antibacterial action tests show that 1 and 2 have better antibacterial activities to Candida albicans than to Escherichia coli or Staphylococcus aureus. In addition, complex 2 has better antibacterial action to Candida albicans than complex 1.

Crystal structure of a hydroxo-bridged dimeric uranyl complex with a 2,2′:6′,2″-terpyridine ligand

A new dimeric compound [{UO2(μ-OH)(terpy)}2](ClO4)2·0.67CH3CN, containing an uranyl cation and a tridentate 2,2′:6′,2″-terpyridine (terpy) ligand, is synthesized from an acetonitrile solution of uranyl perchlorate and terpy. The crystal structure of the compound is determined by single crystal X-ray diffraction. The crystal structure shows the formation of symmetric and asymmetric cationic hydroxo-bridged uranyl dimers. The uranium atoms adopt a distorted pentagonal bipyramidal configuration with a UO4N3 coordination environment formed by two uranyl O atoms, three N atoms from the terpy ligand, and two O atoms from the hydroxide anions.