Joseph Ziller

University of California, Irvine | UCI ·  Department of Chemistry

Symmetric (thio)urea and an unsymmetric urea functionalized salen complexes of Ni(II) were synthesized and studied for anion binding using 1H and 19F NMR spectroscopy and DOSY NMR experiments.

Although there are few reduced dinitrogen complexes of scandium, this metal has revealed a new structural type in reductive dinitrogen chemistry by reduction of bis(pentamethylcyclopentadienyl) scandium halides under N2. Reduction of (Cp* = C5Me5) with potassium graphite (KC8) under dinitrogen generates the dark blue paramagnetic complex , 1. This...

Helicity in solids often arises from the precise ordering of cooperative intra- and intermolecular interactions unique to natural, organic or molecular systems. This exclusivity limited the realization of helicity and its ensuing properties in dense inorganic solids. Here we report that Ga atoms in GaSeI, a representative III–VI–VII one-dimensional...

The complex non-centrosymmetric and chiral nature of helical structures endow materials that possess such motifs with unusual properties. However, despite their ubiquity in biological and organic systems, there is a severe lack of inorganic crystals that display helicity in extended lattices, where these unusual properties are expected to be most p...

The complex non-centrosymmetric and chiral nature of helical structures endow materials that possess such motifs with unusual properties. However, despite their ubiquity in biological and organic systems, there is a severe lack of inorganic crystals that display helicity in extended lattices where these unusual properties are expected to be most pr...

To expand the range of donor atoms known to stabilize 4fn5d1 Ln(II) rare-earth metal (Ln) ions beyond the C, N, and O first row main group donor atoms, the Ln(III) sulfur donor terphenylthiolate iodide complexes, LnIII(SAriPr6)2I (AriPr6 = C6H3-2,6-(C6H2-2,4,6-iPr3)2, Ln = La, Nd) were reduced to form LnII(SAriPr6)2 complexes. These Ln(II) species...

Escalating levels of carbon dioxide (CO2) in the atmosphere have motivated interest in CO2 capture and concentration from dilute streams. A guanidino-functionalized aromatic 1,4-bis(tetramethylguanidino)benzene (1,4-btmgb) was evaluated both as a redox-active sorbent and as a pH swing mediator for electrochemical CO2 capture and concentration. Spec...

Exploration of the reduction chemistry of the 2,2’‐bipyridine (bipy) lanthanide metallocene complexes Cp*2LnCl(bipy) and Cp*2Ln(bipy) (Cp* = C5Me5) resulted in the isolation of a series of complexes with unusual composition and structure including complexes with a single Cp* ligand, multiple azide ligands, and bipy ligands with close parallel orien...

Helicity in atomic scale structures often arises from the precise ordering of cooperative intra- and inter-molecular bonding interactions. The exclusivity of these interactions to natural, organic, or molecular systems has limited the demonstration and understanding of helical motifs in densely packed solid-state lattices. Herein, we report that th...

Thermochromism, the change in color of a material with temperature, is the fundamental basis of optical thermometry. A longstanding challenge in realizing sensitive optical thermometers for widespread use is identifying materials with pronounced thermometric optical performance in the visible range. Herein, it is demonstrated that single crystals o...

The fine-tuning of topologically protected states in quantum materials holds great promise for novel electronic devices. However, there are limited methods that allow for the controlled and efficient modulation of the crystal lattice while simultaneously monitoring the changes in the electronic structure within a single sample. Here, we apply signi...

Metalloproteins with dinuclear cores are known to bind and activate dioxygen, with a subclass of these proteins having active sites containing FeMn cofactors and activities ranging from long-range proton-coupled electron transfer (PCET) to post-translational peptide modification. While mechanistic studies propose that these metallocofactors access...

Thermochromism, the change in color of a material with temperature, is the fundamental basis of optical thermometry. A longstanding challenge in realizing sensitive optical thermometers for widespread use is identifying materials with pronounced thermometric optical performance in the visible range. To this end, we demonstrate that single crystals...

Escalating levels of carbon dioxide (CO2) in the atmosphere have motivated interest in CO2 capture and concentration from dilute streams. A guanidino-functionalized aromatic 1,4-bis(tetramethylguanidino)benzene (1,4-btmgb) was evaluated both as a redox-active sorbent and pH swing mediator for electrochemical CO2 capture and concentration. Spectrosc...

Non-heme Fe monooxygenases activate C–H bonds using intermediates with high-spin FeIV–oxido centers. To mimic these sites, a new tripodal ligand [pop]3− was prepared that contains three phosphoryl amido groups that are capable of stabilizing metal centers in high oxidation states. The ligand was used to generate [FeIVpop(O)]−, a new FeIV–oxido comp...

The reduction of a bimetallic yttrium ansa-metallocene hydride was examined to explore the possible formation of Y-Y bonds with 4d1 Y(II) ions. The precursor [CpAnY(μ-H)(THF)]2 (CpAn = Me2Si[C5H3(SiMe3)-3]2) was synthesized by hydrogenolysis of the allyl complex CpAnY(η3-C3H5)(THF), which was prepared from (C3H5)MgCl and [CpAnY(μ-Cl)]2. Treatment o...

Controlling materials to create and tune topological phases of matter could potentially be used to explore new phases of topological quantum matter and to create novel devices where the carriers are topologically protected. It has been demonstrated that a trivial insulator can be converted into a topological state by modulating the spin-orbit inter...

The high reactivity accessible from the reduction of the tris(amide) complexes Ln(NR2)3 (R = SiMe3) with potassium graphite in the presence of a variety of ethers is demonstrated by crystal structures of six different types of products of C-O bond cleavage reactions with Ln = Y, Ho, Er, and Lu. Specifically, 1,2-dimethoxyethane (DME) can be cleaved...

Reactions of 1,3,5-trimethyl-triazacyclohexane (Me3tach) with common rare-earth metal iodide, chloride, and triflate salts were examined to determine the capacity of this inexpensive chelate to provide alternative precursors for THF-free reactions. The reaction of LaI3(THF)4 and CeI3(THF)4 with 1,3,5-trimethyl-triazacyclohexane in THF generated tol...

Mixed-valence complexes represent an enticing class of coordination compounds to interrogate electron transfer confined within a molecular framework. The diamagnetic heterotrimetallic anion, [V(SNS)2{Ni(dppe)}2]-, was prepared by reducing (dppe)NiCl2 in the presence of the chelating metalloligand [V(SNS)2]- [dppe = bis(diphenylphosphino)ethane; (SN...

The sterically bulky aryloxide ligand OAr* (OAr* = -OC6H2-Ad2-2,6tBu-4; Ad = 1-adamantyl) has been used to generate Ln(II) complexes across the lanthanide series that are more thermally stable than complexes of any other ligand system reported to date for 4fnd1 Ln(II) ions. The Ln(III) precursors Ln(OAr*)3 (1-Ln) were synthesized by reacting 1.2 eq...

1,3,5-Trimethyl-1,3,5-triazacyclohexane (Me3tach) readily complexes uranium triiodide to form (Me3tach)2UI3. The complex is soluble in THF and arenes and can function as a source of UI3 to form organometallic U(III) complexes. When dissolved in pyridine (py), (Me3tach)2UI3 forms (Me3tach)UI3(py)2. A related complex with the larger 1,4,7-trimethyl-1...

The salt metathesis reaction between one equivalent of SmI2(THF)2 and two equivalents of K(C5Me4H) in THF afforded single crystals of the unusual, toluene-soluble, and asymmetric bimetallic Sm(II)/Sm(II) complex, (C5Me4H)2SmII(μ-η3:η5-C5Me4H)SmII(C5Me4H)(THF)2, instead of the expected product, (C5Me4H)2SmII(THF)2. The toluene-insoluble products of...

Bexarotene is an FDA-approved drug for the treatment of cutaneous T-cell lymphoma (CTCL); however, its use provokes or disrupts other retinoid-X-receptor (RXR)-dependent nuclear receptor pathways and thereby incites side effects including hypothyroidism and raised triglycerides. Two novel bexarotene analogs, as well as three unique CD3254 analogs a...

Examination of the reduction chemistry of Nd(NR2)3 (R = SiMe3) under N2 has provided connections between the in situ Ln(III)-based LnIII(NR2)3/K reductions of N2 that form side-on bound neutral (N=N)2- complexes, [(R2N)2(THF)Ln]2[μ-η2:η2-N2], and the Ln(II)-based [LnII(NR2)3]1- reductions by Sc, Gd, and Tb that form end-on bound (N=N)2- complexes,...

1,3,5-Trimethyltriazacyclohexane, Me3tach, readily adds to bismuth triiodide to form a variety of new coordination compounds depending on the stoichiometry, solvent, and crystallization conditions. X-ray crystallographic evidence has been obtained for both 2:1 and 1:1 Me3tach:Bi complexes with formulas of [(Me3tach)2BiI2][(Me3tach)BiI4], [(Me3tach)...

Heteroleptic U(III) complexes supported by bis(cyclopentadienyl) frameworks have been synthesized to examine their suitability as precursors to U(II) complexes. The newly synthesized (C5Me5)2U(OC6H2tBu2-2,6-Me-4), (C5Me5)2U(OC6H2Ad2-2,6-tBu-4) (Ad = 1-adamantyl), (C5Me5)2U(C5H5), and (C5Me5)2U(C5Me4H) are compared with (C5Me5)2U[N(SiMe3)2], (C5Me5)...

Spins in molecules are particularly attractive targets for next-generation quantum technologies, enabling chemically programmable qubits and potential for scale-up via self-assembly. Here we report the observation of one of the largest hyperfine interactions for a molecular system, Aiso = 3,467 ± 50 MHz, as well as a very large associated clock tra...

The reaction of UI3 with NaC5Ph5 in THF generated (η5-C5Ph5)UI2(THF)2 which was characterized by X-ray crystallography. The complex has a four-legged piano stool structure with a 2.539 Å U– (C5Ph5 ring centroid) distance that is slightly longer than the 2.504 Å distance in (η5-C5Me5)UI2(THF)3 which has a larger formal coordination number. Although...

Local electric fields can alter energy landscapes to impart enhanced reactivity in enzymes and at surfaces. Similar fields can be generated in molecular systems using charged functionalities. Manganese(V) salen nitrido complexes (salen = N,N'-ethylenebis(salicylideneaminato)) appended with a crown ether unit containing Na+ (1-Na), K+, (1-K), Ba2+ (...

The U(V) imido complex (C 5 Me 5 ) 2 U VI (=NSiMe 3 ), 1 , was crystallographically characterized from the reaction of (C 5 Me 5 ) 2 U III I(THF) with N 3 SiMe 3 which demonstrates that it can be an intermediate in the reaction which ultimately forms...

Californium (Cf) is currently the heaviest element accessible above microgram quantities. Cf isotopes impose severe experimental challenges due to their scarcity and radiological hazards. Consequently, chemical secrets ranging from the accessibility of 5f/6d valence orbitals to engage in bonding, the role of spin–orbit coupling in electronic struct...

Five novel analogs of 6-(ethyl)(4-isobutoxy-3-isopropylphenyl)amino)nicotinic acid—or NEt-4IB—in addition to seven novel analogs of 4-[1-(3,5,5,8,8-pentamethyl-5,6,7,8-tetrahydro-2-naphthyl)ethynyl]benzoic acid (bexarotene) were prepared and evaluated for selective retinoid-X-receptor (RXR) agonism alongside bexarotene (1), a FDA-approved drug for...

The operational electrochemical potential of a molecular electrocatalyst is typically pinned to the reduction potential of the parent complex. The predominant strategy for minimizing the overpotential is to modify the ligand with electron withdrawing functional groups to anodically shift the reduction potential. However, these changes often result...

The combination of a boron Lewis acid and a decamethylsamarocene, specifically 9,10-Me2-9,10-diboraanthracene with (C5Me5)2SmII(THF)2, in toluene leads to cooperative reductive capture of N2. The product crystallizes as the salt, [(C5Me5)2SmIII(THF)2][(C5Me5)2SmIII(η2-N2B2C14H14)],...

The reductive reactivity of a Ln(II) ion with a nontraditional 4fn5d1 electron configuration has been investigated by studying reactions of the {GdII(N(SiMe3)2)3]}- anion with a variety of reagents that survey the many reaction pathways available to this ion. The chemistry of both [K(18-c-6)2]+ and [K(crypt)]+ salts (18-c-6 = 18-crown-6; crypt = 2....

Local electric fields can alter energy landscapes to impart enhanced reactivity in enzymes and at surfaces. There has been renewed interest on their use in molecular systems, where they can be installed using charged functionalities. Manga-nese(V) salen nitrido complexes (salen = N,N’-ethylenebis(salicylideneaminato)) appended with a crown ether un...

Local electric fields can alter energy landscapes to impart enhanced reactivity in enzymes and at surfaces. There has been renewed interest on their use in molecular systems, where they can be installed using charged functionalities. Manga-nese(V) salen nitrido complexes (salen = N,N’-ethylenebis(salicylideneaminato)) appended with a crown ether un...

The Ba-in-(2.2.2-cryptand) complexes, [Ba(2.2.2-cryptand)(DMF)2][I]2 and [Ba(2.2.2-cryptand)(OTf)2], were synthesized from the reaction of 2.2.2-cryptand with BaI2 and Ba(OTf)2, respectively, and crystallographically characterized for comparison with lanthanide analogs. The complexes are soluble in THF, just as their Ln = Nd and Sm analogs. The rea...

The structure of the title compound, C27H46N2, at 93 K has monoclinic (P21/n) symmetry. The title compound was prepared by treatment of 2-(2,6-diiso­propyl­phenyl)-3,3-dimethyl-2-aza­spiro­[4.5]dec-1-en-2-ium hydrogen dichloride with two equivalents of lithium di­ethyl­amide. Characterization of the title compound by single-crystal X-ray diffractio...

The primary and secondary coordination spheres can have large regulatory effects on the properties of metal complexes. To examine their influences on the properties of monomeric Fe complexes, the tripodal ligand containing phosphinic amido groups, N,N',N''-[nitrilotris(ethane-2,1-diyl)]tris(P,P-diphenylphosphinic amido) ([poat]3-), was used to prep...

The investigation of the coordination chemistry of rare-earth metal complexes with cyanide ligands led to the isolation and crystallographic characterization of the LnIII cyano­tri­phenyl­borate complexes di­chlorido­(cyano­tri­phenyl­borato-κN)tetra­kis­(tetra­hydro­furan-κO)lanthanide(III), [LnCl2(C19H15BN)(C4H8O)4] [lanthanide (Ln) = dysprosium...

We report the synthesis and characterization of the trinuclear 4d-4f compounds [Co(C5Me5)2][(C5Me5)2Ln(μ-S)2Mo(μ-S)2Ln(C5Me5)2], 1-Ln (Ln = Y, Gd, Tb, Dy), containing the highly polarizable MoS43- bridging unit. UV-Vis-NIR diffuse reflectance spectra and DFT calculations of 1-Ln reveal a low-energy metal-to-metal charge transfer transition assigned...

Bimetallic active sites are ubiquitous in metalloenzymes and have sparked investigations of synthetic models to aid in the establishment of structure-function relationship. We previously reported a series of discrete bimetallic complexes with [FeIII-(μ-OH)-MII] cores in which the ligand framework provides distinct binding sites for two metal center...

Electrochemical measurements on tris(cyclopentadienyl)thorium and uranium compounds in the +2, +3, and +4 oxidation states are reported with C5H3(SiMe3)2, C5H4SiMe3, and C5Me4H ligands. The reduction potentials for both U and Th complexes trend with the electron donating abilities of the cyclopentadienyl ligand. Thorium complexes have more negative...

We have validated a general strategy for the synthesis of chloro-containing quinoline, benzoquinoline and polybenzoquinoline variants.

Spins in molecules are particularly attractive targets for next-generation quantum technologies, enabling chemically programmable qubits and potential for scale-up via self-assembly. Here, we demonstrate chemical control of the degree of s-orbital mixing into the spin-bearing d-orbital associated with a series of spin-½ La(II) and Lu(II) molecules....

The nickel(II) complex [ON(H)O]Ni(PPh3) ([ON(H)O]2- = bis(3,5-di-tert-butyl-2-phenoxy)amine), bearing a protonated redox-active ligand, was examined for its ability to serve as a hydrogen atom (H•) and hydride (H-) donor. Deprotonation of [ON(H)O]Ni(PPh3) afforded the square-planar anion {[ONOcat]Ni(PPh3)}1-, whereas hydrogen atom transfer from [ON...

The ligand-centered hydrogen-atom-transfer (HAT) reactivity was examined for a family of group 10 metal complexes containing a tridentate pincer ligand derived from bis(2-mercapto-p-tolyl)amine, [SNS]H3. Six new metal complexes of palladium and platinum were synthesized with the [SNS] ligand platform in different redox and protonation states to com...

Eight cyclopentadienyl U(III) iodide complexes have been synthesized from UI3 and crystallographically characterized to show the variations that can occur with this ligand set and uranium in the +3 oxidation state: (C5Me5)2UI(THF), {[K(OEt2)2][(C5Me5)2U(µ–I)2]}2, [K(18-crown-6)][(C5Me5)2U(µ–I)2], [K(2.2.2-cryptand)][(C5Me5)2UI2], [Li(THF)4][(C5Me5)...

The electrochemical properties of U(III)-in-crypt (crypt = 2.2.2-cryptand) were examined in dimethylformamide (DMF) and acetonitrile (MeCN) to determine the oxidative stability offered by crypt as a ligand. Cyclic voltammetry revealed a U(III)/U(IV) irreversible oxidation at EPA= -0.49 V (vs Fe(C5H5)2+/0) in DMF and at EPA= -0.31 V (vs Fe(C5H5)2+/0...

The 2.2.2-cryptand ligand (crypt) that is heavily used in reductions of rare-earth metal complexes to encapsulate alkali metals has been found to function as a bidentate ligand to rare-earth metal ions in some cases. The X-ray crystal structures of the reduced dinitrogen metal complex, [{(R2N)2Ce(crypt-κ²-O,O′)}2(μ–η²:η²-N2)] (R = SiMe3), and the y...

Studies of the coordination chemistry between the di­phenyl­amide ligand, NPh2, and the smaller rare-earth LnIII ions, Ln = Y, Dy, and Er, led to the structural characterization by single-crystal X-ray diffraction crystallography of both solvated and unsolvated complexes, namely, tris­(di­phenyl­amido-κN)bis­(tetrahydro­furan-κO)yttrium(III), Y(NPh...

Lanthanide triflates have been used to incorporate NdIII and SmIII ions into the 2.2.2‐cryptand ligand (crypt) to explore their reductive chemistry. The Ln(OTf)3 complexes (Ln=Nd, Sm; OTf=SO3CF3) react with crypt in THF to form the THF‐soluble complexes [LnIII(crypt)(OTf)2][OTf] with two triflates bound to the metal encapsulated in the crypt. Reduc...

The green compound poly[(tetra­hydro­furan)­tris­[μ-η⁵:η⁵-1-(tri­methyl­sil­yl)cyclo­penta­dien­yl]caesium(I)ytterbium(II)], [CsYb(C8H13Si)3(C4H8O)]n or [(THF)Cs(μ-η⁵:η⁵-Cp′)3YbII]n was synthesized by reduction of a red THF solution of (C5H4SiMe3)3YbIII with excess Cs metal and identified by X-ray diffraction. The compound crystallizes as a two-dim...

N,N′-Di-tert-butyl­carbodi­imide, Me3CN=C=NCMe3, undergoes reductive cleavage in the presence of the GdII complex, [K(18-crown-6)2][GdII(NR2)3] (R = SiMe3), to form a new type of ligand, the tert-butyl­cyanamide anion, (Me3CNCN)⁻. This new ligand can bind metals with one or two donor atoms as demonstrated by the isolation of a single crystal contai...