Ligand Substituents Research Articles

Correlation between Supramolecular Connectivity and Magnetic Behaviour of [FeIII(5-X-qsal)2]+-Based Salts Prone to Exhibit SCO Transition

We present an extensive study to determine the relationship between structural features of spin crossover (SCO) systems based on N-(8-quinolyl)salicylaldimine (qsal) ligand derivatives and their magnetic properties. Thirteen new compounds with general formula [FeIII(5-X-qsal)2]+ (X = H, F, Cl, Br and I) coupled to Cl−, ClO4−, SCN−, PF6−, BF4− and BPh4− anions were prepared and magnetically characterized. The structure/properties correlations observed in these compounds were compared to those of salts with the same [FeIII(qsal-X)2]+ cations previously reported in the literature. These cations favour the LS configuration in compounds with the weakest connectivity. As connectivity increases most of them present HS states at room temperature and structures may be described as arrangements of parallel layers of interacting cation dimers. All the compounds based on these cations undergoing complete SCO transitions within the 4–300 K temperature range have high intralayer connectivity. If, however, the interlayer connectivity becomes very strong they remain blocked in the HS or in the LS state. The SCO transition may be affected by the slightest change of solvent molecules content, disorder or even crystallinity of the sample and it remain difficult to predict which kind of ligand substituent should be selected to obtain compounds with the desired connectivity.

First row transition metal complexes of bis(3,5-dimethyl pyrazolyl)methane: Synthesis, molecular structure and antibacterial properties

A series of nine transition metal complexes was synthesized by reacting bis(3,5-dimethylpyrazolyl)methane (BP) with the respective metal chlorides in 1:1 and 2:1 stochiometric proportions. The complexes were duly characterized by molar conductivity measurement, IR, UV, NMR spectroscopy and elemental analysis. Using X-ray analysis, solid state molecular structures of the complexes C3 and C8 were determined. The molecular structures and the stoichiometry of the obtained complexes were found to be governed by the steric factors of the ligand substituents. The prepared compounds were found to be bactericidal against the four bacterial stains tested, however with high MIC/MBC values.

Abrupt Spin-State Switching in Mn(III) Complexes with BPh4 Anion: Effect of Halide Substituents on Crystal Structure and Magnetic Properties.

Three tetraphenylborates of mononuclear Mn(III) cation complexes with hexadentate ligands, the products of the reaction between a N,N'-bis(3-aminopropyl)ethylenediamine and salicylaldehydes with the different haloid substitutions at the 5 or 3,5 positions, have been synthesized: [Mn(5-F-sal-N-1,5,8,12)]BPh4 (1), [Mn(3,5-diCl-sal-N-1,5,8,12)]BPh4 (2) and [Mn(3,5-Br,Cl-sal-N-1,5,8,12)]BPh4 (3). Their crystal structure, dielectric constant (ϵ) and magnetic properties have been studied. Ligand substituents have a dramatic effect on the structure and magnetic properties of the complexes. With decreasing temperature, the complex (1) shows a gradual spin crossover from the high-spin state (HS) to the HS:LS intermediate phase, followed by an abrupt transition to the low-spin state (LS) without changing the crystal symmetry. The complexes 2 and 3 are isostructural, but have fundamentally different properties. Complex 2 demonstrates two structural phase transitions related to sharp spin crossovers from the HS to the HS:LS intermediate phase at 137 K and from the intermediate phase to the LS at 87 K, while complex 3 exhibits only one spin transition from the HS to the HS:LS intermediate phase at 83 K.

Nickel-Templated Replacement of Phosphine Substituents in a Tetradentate Bis(amido)bis(phosphine) Ligand.

The replacement of phosphine substituents in nickel-bound PNNP ligands is reported as an alternative method for preparing multidentate phosphine ligands with alkyl substituents. Treatment of the previously reported bis(phosphide) complex {K(THF)x}22Ph[PNNP]Ni (2) with 2 equiv of MeI, iPrI, and 1,3-dibromoethane formed alkyl-substituted complexes 2Ph,2Me[PNNP]Ni (3), 2Ph,2iPr[PNNP]Ni (4), and 2Ph,propylene[PNNP]Ni (5), respectively. The stereoselectivity (racemic vs meso) of these reactions can be controlled by varying the reaction temperature. The racemic mixtures of products with the new alkyl substituents in an anti configuration were favored at lower temperatures, whereas a larger proportion of meso compounds was acquired at higher temperatures. Further treatment of 3 with KH resulted in selective elimination of the remaining phenyl groups rather than the methyl substituents, affording bis(methylphosphide) complex {K(THF)x}22Me[PNNP]Ni (6). Subsequent treatment of 6 with additional MeI formed 4Me[PNNP]Ni (7), in which all four phenyl groups were replaced with methyl substituents. As a proof of concept, demetalation of the ligand from 7 was achieved using aqueous KCN to form a free dimethylphosphine-substituted ligand H24Me[PNNP] (8), and 8 was subsequently coordinated to a different metal, using PdCl2 to form 4Me[PNNP]Pd (9). Unlike the clean elimination of phenyl substituents from 3, the reactions of KH with 4 and 5 exhibited competitive elimination of both alkyl and phenyl substituents and/or attenuated reactivity.

Lithium Half‐Salen Complexes: Synthesis, Structural Characterization and Studies as Catalysts for rac‐Lactide Ring‐Opening Polymerization

AbstractSeven lithium complexes supported by sterically and electronically diverse phenoxyimine ligands were synthesized and characterized by X‐ray diffraction, NMR spectroscopy and elemental microanalysis. These complexes show high activity (kobs ≤7.43×10−2 s−1) for rac‐lactide ring‐opening polymerization (ROP) in the presence of co‐initiator benzyl alcohol (BnOH), with the exception of Li4 which features an unusual polymeric ladder structure. Overall, the catalyst activity correlates to the aggregation state; the catalysts with low aggregation states display increased propagation rates attributed to improved metal accessibility and kinetic mobility. The nature of the ligand substituents and solvent influence the catalyst aggregation in both the solid‐ and solution‐state. While the lithium complexes can initiate rac‐lactide ROP without BnOH, the addition of this co‐initiator significantly increases the polymerization rate by switching the mechanism from a coordination‐insertion to an activated monomer pathway, changing the resultant poly(lactic acid) architecture from cyclic to linear.

A Series of High-Nuclear Gadolinium Cluster Aggregates with a Magnetocaloric Effect Constructed through Two-Component Manipulation.

The serialized expansion of high-nuclear clusters usually includes the controlled variable method and changes only a single variable. However, changing both variables will greatly increase the complexity of the reaction simultaneously. Therefore, the use of a two-component regulation reaction is rare. Herein, we used a diacylhydrazone ligand (H4L1) with multidentate chelating coordination sites for the reaction with Gd(NO3)3·6H2O under solvothermal conditions to obtain an example of 16-nucleus disc-shaped cluster 1 with a brucite structure. The overall structure of cluster 1 can be regarded as an equilateral triangle, which is formed by three (L1)4- ions that can be regarded as "sides" and wrap the four-layer metal center Gd(III) ions. Notably, upon simultaneous regulation of the substituent of the ligand and the coordination anion, heptanuclear gadolinium cluster 2 was obtained. Cluster 2 can be regarded as a butterfly structure, which was formed by connecting two Gd3L2 molecules that were not in the same plane and through the central Gd(III) ion as an intersection. Moreover, hexanuclear gadolinium cluster 3 was obtained by changing the ligand substituent and adding an auxiliary ligand. Cluster 3 can be regarded as a chair structure, which was composed of two molecules of diacylhydrazone ligand (L2)4- wrapping vacant cubane shared by four vertices. This study was the first to construct a series of high-nuclear gadolinium clusters through two-component regulation manipulation. The study of the magnetocaloric effect showed that the maximum values of -ΔSm for clusters 1-3 were 34.05, 29.04, and 24.32 J kg-1 K-1, respectively, when T = 2 K and ΔH = 7 T.

Arylamination via ortho-fusion on an azo-appended pyridine carboxamide complex of copper(II)

A square-pyramidal complex [CuII(L)(O2CMe)(H2O)] 1 (HL = 2–[N–(2–phenylazo)carbamoyl]pyridine) has been synthesized using a tridentate deprotonated arylazo-appended pyridine-2-carboxamide ligand. Aerobic reactions of 1 with para-substituted anilines in neat condition at 120 °C afforded isolation of its ortho-arylaminated products [CuII(L−N−C6H4−p−X)] (X = H 2, Me 3, OMe 4, F 5 and Cl 6). The starting brown complex 1 and arylaminated violet complexes 2−6 have been structurally characterized. The electronic spectral feature and redox properties of 1−6 have been examined. Along with CuII/CuI redox, azo-centered cathodic responses were also observed. For 2–6, a characteristic oxidative response due to Cu(II)-coordinated amine oxidation has been observed, modulated by ligand substituents. A linear correlation between the redox potential values of the arylaminated products 2–6 and the Hammett substituent constant σp for para-substituted anilines has been obtained, to rationalize the proposed mechanistic pathways of the observed ortho-fusion reaction. Density functional theory (DFT) at the B3LYP level and time-dependent (TD)-DFT calculations have allowed to rationalize the experimental results and to interpret the observed electronic transitions, respectively.

Synthesis of highly branched polyethylene and ethylene-MA copolymers using hybrid bulky α-diimine Pd(II) catalysts

The types and sizes of N-o-aryl substituents in the α-diimine ligands strongly influence the ethylene (co)polymerization. Also, the combination of different substituents may play an unexpected role. A new class of bulky unsymmetrical acenaphthene-based α-diimine Pd(II) catalysts utilizing bulky “hybrid” anilines were designed, synthesized and characterized in this study. In ethylene polymerization, the α-diimine Pd(II) catalysts exhibited moderate activities, generating highly branched polyethylene with reasonable molecular weight. Moreover, these Pd(II) catalysts were also capable of preparing polar functionalized E-MA copolymers with moderate molecular weights and high incorporation ratios in the copolymerization of ethylene with methyl acrylate. Notably, compared to symmetrical bulky Pd(II) catalysts, the “hybrid” unsymmetrical system produced highly branched polyethylene and E-MA copolymers significantly.

Chromium catalysts based on PNP(NR2)2 ligands for selective ethylene oligomerization

High active and selective 1–3 chromium catalysts based on the corresponding Ph2PN(cyclopentyl)P (NR2)2‐type L1–L3 ligands (L1: R = methyl, L2: R = ethyl, L3: R = isopropyl) have been explored for selective ethylene tri‐/tetramerization. We found that the ligand substituents and the experimental conditions considerably influenced the catalytic performance of 1–3 based catalysts. Combining a higher ethylene pressure can elevate the selectivity of 1‐octene (67.98%) of precatalyst 1 with high catalytic activity (9.3 × 106 g/[molCr h]). Furthermore, precatalysts 2–3 efficiently offer selective ethylene trimerization and afforded 97.76% 1‐hexene selectivity with 5.8 × 106 g/(molCr h) catalytic activity (in case precatalyst 3). A relatively low catalyst mass, high Al/Cr molar ratio, and high ethylene pressure display excellent catalytic activity and selectivity for ethylene oligomerization.

Cobalt‐Catalysed, Ligand‐Controlled Regiodivergent Alkene Hydrosilylation

AbstractAlkene hydrosilylation is amongst the largest industrial homogenous catalysis processes. Cobalt catalysis offers a sustainable alternative to commonly used platinum catalysts to achieve this transformation. Using two bisiminopyridine cobalt(II) catalysts the regiodivergent hydrosilylation of alkenes has been developed. Variation of pre‐catalyst activator and ligand substituents were investigated to enable the controlled, regiodivergent hydrosilylation of both aryl‐ and alkyl‐substituted alkenes with phenylsilane. In contrast to other regiodivergence strategies, excellent regioselectivity for either isomer was achieved using the same ligand class but differing by a single methyl group (ethyl vs isopropyl).

Heterogeneous Molecular Catalysts of Metal Phthalocyanines for Electrochemical CO2 Reduction Reactions.

ConspectusMolecular catalysts, often deployed in homogeneous conditions, are favorable systems for structure-reactivity correlation studies of electrochemical reactions because of their well-defined active site structures and ease of mechanistic investigation. In pursuit of selective and active electrocatalysts for the CO2 reduction reactions which are promising for converting carbon emissions to useful fuels and chemical products, it is desirable to support molecular catalysts on substrates because heterogeneous catalysts can afford the high current density and operational convenience that practical electrolyzers require. Herein, we share our understanding in the development of heterogenized metal phthalocyanine catalysts for the electrochemical reduction of CO2. From the optimization of preparation methods and material structures for the electrocatalytic activity toward CO2 reduction to CO, we find that molecular-level dispersion of the active material and high electrical conductivity of the support are among the most important factors controlling the activity. The molecular nature of the active site enables mechanism-based optimization. We demonstrate how electron-withdrawing and -donating ligand substituents can be utilized to modify the redox property of the molecule and improve its catalytic activity and stability. Adjusting these factors further allows us to achieve electrochemical reduction of CO2 to methanol with appreciable activity, which has not been attainable by conventional molecular catalysts. The six-electron reduction process goes through CO as the key intermediate. Rapid and continuous electron delivery to the active site favors further reduction of CO to methanol. We also point out that, in homogeneous electrocatalysis where the catalyst molecules are dissolved in the electrolyte solution, even if the molecular structure remains intact, the actual catalysis may be dominated by molecules permanently adsorbed on the electrode surface and is thus heterogeneous in nature. This account uses our research on CO2 electroreduction reactions catalyzed by metal phthalocyanine molecules to illustrate our understanding about heterogeneous molecular electrocatalysis, which is also applicable to other electrochemical systems.

Guest‐selective gate‐opening by pore engineering of two‐dimensional Kagomè lattice porous coordination polymers

AbstractPorous coordination polymers (PCPs) with pore decoration have been used as materials for excellent storage and separation functions. The cooperative properties of flexible PCPs can be utilized to achieve the separation of mixtures of gaseous molecules having highly similar properties. The key to efficient molecular recognition and separation lies in increasing the degrees of freedom of the structure without sacrificing the stability of the system. However, the mechanism study of such behavior is still scarce in the literature. Here, we focused on PCPs with two‐dimensional Kagomè lattice structures and functionalized the pores with various alkoxy pendant groups; this facilitated systematic tuning of the pore aperture size, the interlayer spacing, as well as the interactions between the host and adsorbed molecules. The combination of characterization techniques allowed us to observe a unique deformation of the lattice upon gas sorption, allowing the separation of gas molecules with similar physicochemical properties, such as propane and propylene.Key pointsFlexible porous coordination polymers (PCPs) can create an excellent mechanism for recognizing gases with very similar properties. Here, PCPs with a Kagomè framework, in which hexagonal (H) and triangular (T) pores are adjacent to each other, can achieve a high level of propylene/propane separation by controlling the cooperativity of the H‐T pores with ligand substituents.

Ruthenium Dye Excitations and Relaxations in Natural Sunlight.

Solar harvesting devices using dyes convert the sun's energy to usable forms. The photophysics involved are generally investigated using time-resolved spectroscopic experiments with femtosecond to nanosecond resolution. We show that a kinetic framework constructed from transient and linear absorption measurements of metal-ligand charge transfer states for a set of ruthenium complexes in solution can be used to simulate the steady-state dynamics of dyes adsorbed on a substrate under diffuse solar radiation. Even though the intensity of sunlight is relatively low, double excitations to higher excited states can occur. The steady-state populations show that the dyes' triplet state is the main species present besides the ground state. While small, these persistent excited populations can influence reactivity over the extended periods of time that the systems operate. The results show that non-radiative and optical events (dye-1 s-1) within the singlet manifold and from the triplet state exhibit a dependence on ligand substituents.

NOVEL NON-AQUEOUS ELECTROLYTES BASED ON COORDINATION BORON COMPOUNDS

The review provides a classification of electrolytes for modern chemical power sources, supercapacitors, sodium and lithium-ion batteries depending on changes in the physicochemical properties of salts and the products of their interaction with the solvent. A comparative analysis of physicochemical properties of salts depending on the structure of the cation and anion, and the influence of these properties on the properties of final solutions of electrolytes on the example of different classes of ionic liquids and chelatoborates of alkali metals and ammonium was conducted. The dependence of the physicochemical properties of electrolytes (solubility, electrical conductivity of solutions and the range of potentials of electrochemical stability) on the nature of the chelate ligand, electron donor and electroacceptor substituents in the bis (chelate) borate anion is analyzed. The electrical conductivity of salt solutions and ranges of potentials of electrochemical stability of the corresponding electrolytes containing other anions and used for a long time in chemical current sources are carried out. The advantages and disadvantages of using liquid electrolytes compared to solid and polymer electrolytes in terms of similarity of their structures have been detected. It is shown that the nature of the chelate ligand, electro-donor and electro-acceptor substituents in the bis (chelato) borate anion is an important factor in regulating the interaction with aprotic dipolar solvents. Mixed salts with two different chelate ligands typically combine the best characteristics of the corresponding monochelate compounds, but the methods for their preparation and purification are technologically significantly more complex compared to monochelate compounds. The analysis of the mechanism of formation of a protective film on a surface of electrode materials, dependence of potential on its formation and on the chemical nature of ligands is made. It is noted that bis (chelato) borate salts are more environmentally friendly compared to fluorine-containing complex salts. Emphasis is placed on the physicochemical properties of solutions of the most promising chelatoborate salts for use in lithium and sodium ion batteries, supercapacitors and electrolytic capacitors, and it is shown that bis (oxalate) borates and bis (salicylate gold) borates occupy ) borates in terms of electrical conductivity, solubility and potential range of electrochemical stability.

Electronic structures, bonding and energetics of non-heme mono and dinuclear iron-TPA complexes: a computational exploration

Due to their rich structural chemistry and enormous catalytic applications, TPA (tris(2-pyridylmethyl)amine) coordinated iron (Fe-TPA) complexes are widely studied as potent functional model in biomimetic area. We have done a thorough computational study on six diverse mononuclear and dinuclear FeII/FeIII-TPA complexes using density functional method. All the possible spin states for the six species were computed, and the ground state S value of these species was determined. The molecular structures, energetic profiles of spin states, electrostatic potentials, spin densities, and orbital energies of all the six complexes are reported. A comparative study among these six species was also done to gain insights about any sort of correlation in properties of these species. The observed variations as well as correlations in properties of the species are imputed to the diverse ligand substituents in Fe-TPA skeleton. Theoretical reactivity behavior was evaluated by doing frontier molecular orbital analysis for all the species by mapping HOMO-LUMO diagrams. Electrostatic potential surfaces were mapped to study charge energy distribution in the species. Our computed results are in well agreement with the experimental data.

Amidinate Supporting Ligands Influence Molecularity in Formation of Uranium Nitrides.

Uranium nitride complexes are attractive targets for chemists as molecular models for the bonding, reactivity, and magnetic properties of next-generation nuclear fuels, but these molecules are uncommon and can be difficult to isolate due to their high reactivity. Here, we describe the synthesis of three new multinuclear uranium nitride complexes, [U(BCMA)2]2(μ-N)(μ-κ1:κ1-BCMA) (7), [(U(BIMA)2)2(μ-N)(μ-NiPr)(K2(μ-η3:η3-CH2CHNiPr)]2 (8), and [U(BIMA)2]2(μ-N)(μ-κ1:κ1-BIMA) (9) (BCMA = N,N-bis(cyclohexyl)methylamidinate, BIMA = N,N-bis(iso-propyl)methylamidinate), from U(III) and U(IV) amidinate precursors. By varying the amidinate ligand substituents and azide source, we were able to influence the composition and size of these nitride complexes. 15N isotopic labeling experiments confirmed the bridging nitride moieties in 7-9 were formed via two-electron reduction of azide. The tetra-uranium cluster 8 was isolated in 99% yield via reductive cleavage of the amidinate ligands; this unusual molecule contains nitrogen-based ligands with formal 1-, 2-, and 3- charges. Additionally, chemical oxidation of the U(IV) precursor U(N3)(BCMA)3 yielded the cationic U(V) species [U(N3)(BCMA)3][OTf]. Magnetic susceptibility measurements confirmed a U(IV) oxidation state for the uranium centers in the three nitride-bridged complexes and provided a comparison of magnetic behavior in the structurally related U(III)-U(IV)-U(V) series U(BCMA)3, U(N3)(BCMA)3, and [U(N3)(BCMA)3][OTf]. At 240 K, the magnetic moments in this series decreased with increasing oxidation state, i.e., U(III) > U(IV) > U(V); this trend follows the decreasing number of 5f valence electrons along this series.

Elaborate Design of d8-d10 Heteronuclear Phosphors for Ultrahigh-Efficiency Solution-Processed Organic Light-Emitting Diodes.

Highly soluble d8-d10 heteronuclear phosphors afford an alternative approach to achieve high-efficiency organic light-emitting diodes (OLEDs) through a solution process. In this work, four highly phosphorescent d8-d10 heteronuclear complexes with significant Pt-Au interactions were prepared. By judicious selection of sterically hindered and π-conjugated substituents in triphosphine ligands, the phosphorescence is dramatically promoted through effectively prohibiting nonradiative thermal relaxation with an efficiency of 0.94-0.99 in doping films. Exploiting highly emissive Pt-Au complexes as phosphorescent dopants, ultrahigh-efficiency solution-processed OLEDs were attained. The peak current efficiency, power efficiency, and external quantum efficiency are 96.2 cd A-1, 65.0 lm W-1, and 26.4% for the green-emitting PtAu2 phosphor and 68.6 cd A-1, 42.5 lm W-1, and 25.1% for the orange-emitting Pt2Au phosphor, which represent the state-of-art for solution-processed OLEDs based on non-iridium phosphors.

Rational design and synthesis of AIE active cationic Ir(III) complexes featuring iminopyridine ligand with dibenzosuberane core

Novel cationic iridium(III) complexes (Ir1–Ir4) composed of iminopyridine ligands with dibenzosuberane core were synthesized. All the designed complexes Ir1–Ir4 were fully characterized through FT-IR, elemental analysis, 1H, 13C, 19F, and 31P NMR. Molecular structures of Ir1 and Ir2 are unambiguously determined by single-crystal XRD studies and thus confirm the distorted-octahedral geometry around the Ir(III) centers. Photophysical properties such as absorption, emission, and photoluminescence quantum yields (PLQYs) of Ir1–Ir4 can be accessibly finely-tuned by varying the substituents of ancillary ligands (N^N). Cyclic voltammetry (CV), and thermogravimetric analysis (TGA) were then performed to investigate the electrochemical and thermal properties of Ir1–Ir4. Solution-state emission spectra of the complexes Ir1–Ir4 showed blue-shifted emission in the range of 433 – 436 nm (PLQYs = 0.19 – 0.62 %) whereas the same complexes displayed red-shifted emission (λ max 626 – 638 nm, PLQYs = 0.31 – 0.65 %) of their solid-state emission spectra. Aggregation-induced emission (AIE) properties of Ir1–Ir4 were analyzed with dichloromethane and hexane solvent mixture. Upon aggregation (99 % of hexane), the emission intensities of Ir1–Ir4 were constantly increased with the increase of hexane concentration. Similarly, the PLQYs and lifetimes of aggregated species of Ir1–Ir4 (PLQYs = 18 – 28 % and τ = 78.8 – 101.3 ns) were excellently improved in contrast to those in pure dichloromethane solutions. Interestingly, the scanning electron microscope (SEM) images of aggregates of Ir2 exposed the hollow polymer type of morphology and such a kind of morphology derived from Ir(III) complex is not reported.

From zero-dimensional complexes to one-dimensional coordination polymers adjusted by the solvents or ligand substituent groups

A new ligand, 6-(4-carboxyphenyl)-3-(2-chloroimidazo[1,2-a]pyridin-3-yl)picolinic acid (H2L1), was used to construct two zero-dimensional (0D) complexes ([Zn(HL1)2] (1) and ([Ni(HL1)2(H2O)2] (3)), and one one-dimensional (1D) zig-zag chain coordination polymer ([Zn(L1)(H2O)2]n (2)) which was further assembled into porous three-dimensional (3D) supramolecular framework. The various dimensionality of 1–3 essentially originates from the types of organic solvents, because protic EtOH solvent resulted in completely deprotonated 2-connected L12− in 2, conversely, polar MeCN only caused partial deprotonation to give 1-connected HL1− in 1 and 3. Moreover, through changing 2-chloroimidazo[1,2-a]pyridine ring to pyridine ring, 0D Ni(II) complex (3) was adjusted to 1D ladder chain Ni(II) coordination polymer ([Ni(L2)(H2O)2]n•2H2O (4)) which should be ascribed to ligand substituent group effects. The photoluminescent or magnetic properties of 1–4 were also researched.

Synthesis and Characterization of Tellurium Catecholates and Their N-Oxide Adducts.

Tellurium catecholate complexes were investigated to probe the redox chemistry of tellurium, whose oxidation state can span from -2 to +6. Treating TeO2 with catechols resulted in tellurium coordination complexes in high yields within minutes to hours at room temperature or with extended heating, depending on the ligand substituents, giving Te(IV) complexes of the form Te(C)2, where C = 3,5-di-tert-butylcatecholate, o-catecholate, or tetrachlorocatecholate. The redox behavior of these complexes was investigated through addition of organic oxidants, giving nearly quantitative adducts of pyridine N-oxide or N-methylmorpholine N-oxide with each tellurium complex, the latter set leading to ligand oxidation upon heating. Each compound was characterized crystallographically and computationally, providing data consistent with a mostly electrostatic interaction and very little covalent character between the N-oxide and Te complex. The Te N-oxide bond orders are consistently lower than those with the catechol derivatives, as characterized with the Mayer, Gopinathan-Jug (G-J), and first Nalewajski-Mrozek (N-M1) bond indices. The tellurium lone pair is energetically buried by 1.93-2.81 eV, correlating with the observation that the ligands are more reactive than the tellurium center toward oxidation. This combined experimental and theoretical study finds structure-property relationships between ligand design and reactivity that will aid in future efforts for the recovery of tellurium.