6-[4-(-Butyl-dimethyl-sil-yloxy)phen-yl]-1-oxa-spiro-[2.5]hepta-ne.

The title compound, CHOSi, has triclinic () symmetry at 100 K. The O atom of the epoxide group has a pseudoaxial orientation and the dihedral angle between the cyclo-hexyl and benzene rings is 85.80 (8)°.

Observation of oxygenated intermediates in functional mimics of aminophenol dioxygenase.

Aminophenol dioxygenases (APDO) are mononuclear nonheme iron enzymes that utilize dioxygen (O) to catalyze the conversion of o-aminophenols to 2-picolinic acid derivatives in metabolic pathways. This study describes the synthesis and O reactivity of two synthetic models of substrate-bound APDO: [Fe(Tp)(APH)] (1) and [Fe(Tp)(APH)] (2), where Tp = hydrotris(3,5-dimethylpyrazole-1-yl)borate, APH = 4,6-di-tert-butyl-2-aminophenolate, and APH = 4-tert-butyl-2-aminophenolate. Both Fe(II) complexes behave as functional APDO mimics, as exposure to O results in oxidative CC bond cleavage of the o-aminophenolate ligand.

Spectroscopic and Magnetic Studies of Co(II) Scorpionate Complexes: Is There a Halide Effect on Magnetic Anisotropy?

The observation of single-molecule magnetism in transition-metal complexes relies on the phenomenon of zero-field splitting (ZFS), which arises from the interplay of spin-orbit coupling (SOC) with ligand-field-induced symmetry lowering. Previous studies have demonstrated that the magnitude of ZFS in complexes with 3d metal ions is sometimes enhanced through coordination with heavy halide ligands (Br and I) that possess large free-atom SOC constants. In this study, we systematically probe this "heavy-atom effect" in high-spin cobalt(II)-halide complexes supported by substituted hydrotris(pyrazol-1-yl)borate ligands (Tp and Tp).

Reversible Dioxygen Binding to Co(II) Complexes with Noninnocent Ligands.

A series of mononuclear Co(II) complexes with noninnocent (redox-active) ligands are prepared that exhibit metal-ligand cooperativity during the reversible binding of O. The complexes have the general formula, [Co()(Tp)] (R = Me, Ph), where is a bidentate -aminothiophenolate and Tp is a hydrotris(pyrazol-1-yl)borate scorpionate with R-substituents at the 3- and 5-positions. Exposure to O at room temperature results in one-electron oxidation and deprotonation of .

Design, Synthesis, Electronic Properties, and X-ray Structural Characterization of Various Modified Electron-Rich Calixarene Derivatives and Their Conversion to Stable Cation Radical Salts.

We have designed and synthesized electron-rich calixarene derivatives, which undergo reversible electrochemical oxidation in a well-accessible potential range that allows the ready preparation and isolation of the corresponding cation radicals. Preparation of mono- or tetra-radical cation can be achieved by using stable aromatic cation-radical salts such as MA, MB, and NAP as selective organic oxidants. The cation radicals of calixarenes are stable indefinitely at ambient temperatures and can be readily characterized by UV-vis-NIR spectroscopy.

Discovery of two novel (4-hydroxyphenyl) substituted polycyclic carbocycles as potent and selective estrogen receptor beta agonists.

Two (4-hydroxyphenyl) substituted polycyclic carbocycles were prepared and assayed for estrogen receptor activity. 4-(4-Hydroxyphenyl)tricyclo[3.3.

Regioselectivity in the Scholl Reaction: Mono and Double [7]Helicenes.

We employed the density functionaly theory (DFT)-predicted regioselectivity of the intramolecular Scholl reaction in phenanthrene and dibenzo[,]chrysene frameworks to obtain π-extended mono and double [7]helicenes, respectively. The formation of these helical structures occurs despite the buildup of a large strain energy up to 30 kcal/mol compared with their most stable isomers. The twisted and strained structures were characterized and analyzed by experimental (NMR, UV-vis, emission, electrochemistry, and single-crystal X-ray diffraction) techniques and were further supported by DFT calculations.

Angular ladder-type -phenylenes: synthesis and electronic structural analysis.

Herein, we report the synthesis of two new series of angular (all-syn) ladder-type -[n]phenylenes (LMP, n = 3-8). One series contains keto groups at the termini bridges, denoted angular keto (AKn), the second contains alkyl groups at all bridge sp carbons, denoted angular alkyl (AAn). Their electronic and structural properties were delineated by a combination of electrochemistry and spectroscopic (UV-Vis and emission) methods and further supported by DFT calculations.

Nonheme iron-thiolate complexes as structural models of sulfoxide synthase active sites.

Two mononuclear iron(ii)-thiolate complexes have been prepared that represent structural models of the nonheme iron enzymes EgtB and OvoA, which catalyze the O2-dependent formation of carbon-sulfur bonds in the biosynthesis of thiohistidine compounds. The series of Fe(ii) complexes reported here feature tripodal N4 chelates (LA and LB) that contain both pyridyl and imidazolyl donors (LA = (1H-imidazol-4-yl)-N,N-bis((pyridin-2-yl)methyl)methanamine; LB = N,N-bis((1-methylimidazol-2-yl)methyl)-2-pyridylmethylamine). Further coordination with monodentate aromatic or aliphatic thiolate ligands yielded the five-coordinate, high-spin Fe(ii) complexes [FeII(LA)(SMes)]BPh4 (1) and [FeII(LB)(SCy)]BPh4 (2), where SMes = 2,4,6-trimethylthiophenolate and SCy = cyclohexanethiolate.

Probing the Magnetic Anisotropy of Co(II) Complexes Featuring Redox-Active Ligands.

Coordination complexes that possess large magnetic anisotropy (otherwise known as zero-field splitting, ZFS) have possible applications in the field of magnetic materials, including single molecule magnets (SMMs). Previous studies have explored the role of coordination number and geometry in controlling the magnetic anisotropy and SMM behavior of high-spin ( = 3/2) Co(II) complexes. Building upon these efforts, the present work examines the impact of ligand oxidation state and structural distortions on the spin states and ZFS parameters of pentacoordinate Co(II) complexes.

Route exploration and synthesis of the reported pyridone-based PDI inhibitor STK076545.

The enzyme protein disulfide isomerase (PDI) is essential for the correct folding of proteins and the activation of certain cell surface receptors, and is a promising target for the treatment of cancer and thrombotic conditions. A previous high-throughput screen identified the commercial compound STK076545 as a promising PDI inhibitor. To confirm its activity and support further biological studies, a resynthesis was pursued of the reported β-keto-amide with an N-alkylated pyridone at the α-position.

Modified Synthesis of the Peptidomimetic Natriuretic Peptide Receptor-C Antagonist M372049.

The Natriuretic Peptide Receptors (NPRs) regulate vascular sodium levels and have been of significant interest for the potential treatment of hypertension and related cardiovascular complications. The peptidomimetic antagonist M372049 is a valuable probe for the study of NPR-C signaling, unfortunately it is presently not commercially available. Described is a detailed protocol for its synthesis that does not require specialized apparatus and builds upon a prior patent from Veale and colleagues.

Spectroscopic and Computational Comparisons of Thiolate-Ligated Ferric Nonheme Complexes to Cysteine Dioxygenase: Second-Sphere Effects on Substrate (Analogue) Positioning.

Parallel spectroscopic and computational studies of iron(III) cysteine dioxygenase (CDO) and synthetic models are presented. The synthetic complexes utilize the ligand tris(4,5-diphenyl-1-methylimidazol-2-yl)phosphine (TIP), which mimics the facial three-histidine triad of CDO and other thiol dioxygenases. In addition to the previously reported [Fe(CysOEt)(TIP)]BPh (; CysOEt is the ethyl ester of anionic l-cysteine), the formation and crystallographic characterization of [Fe(2-MTS)(TIP)]BPh () is reported, where the methyl 2-thiosalicylate anion (2-MTS) resembles the substrate of 3-mercaptopropionate dioxygenase (MDO).

Redox-Induced Molecular Actuators: The Case of Oxy-Alternate Bridged Cyclotetraveratrylene.

We report a practical two-step approach for the synthesis of hybrid-bridge macrocyclic molecules that has been used to synthesize two novel oxy-alternate-bridged macrocyclic molecules, oxy-alternate cyclotetraveratrylene (CTTV) and oxy-alternate cyclohexaveratrylene (CHV). Electrochemistry, absorption spectroscopy, X-ray crystallography, and DFT calculations demonstrate that CTTV acts as a redox-induced molecular actuator, as its switches from the open conformation in the neutral state to the closed conformation in the cation-radical state.

Iron(ii) tetrafluoroborate complexes of new tetradentate C-scorpionates as catalysts for the oxidative cleavage of trans-stilbene with HO.

Attachment of a 2-methylpyridyl group onto the unique 1-nitrogen atom on nitrogen-confused C-scorpionates with either pyrazol-1-yl or 3,5 dimethylpyrazol-1-yl donors gives two new cis-directing tetradentate-N ligands (L and L*). The complexes [(L or L*)Fe(CHCN)](BF) (1 or 2) were prepared, fully characterized, and investigated for their ability to catalyse the oxidative cleaveage of trans-stilbene in CHCN. Complexes 1 and 2 are capable of catalysing stilbene cleavage when HO is used as an oxidant but up to six different products are formed, with C[double bond, length as m-dash]C cleavage products (benzaldehyde and benzoic acid) dominating over four products of oxygen transfer.

Cobalt Superoxo and Alkylperoxo Complexes Derived from Reaction of Ring-Cleaving Dioxygenase Models with O.

The syntheses and O reactivities of active-site models of cobalt-substituted ring-cleaving dioxygenases are presented. The pentacoordinate cobalt(II)-aminophenolate complex, [Co(Tp)(APH)], gives rise to two distinct dioxygen adducts at reduced temperatures. The first is a paramagnetic ( = 1/2) cobalt(III)-superoxo species that was characterized with spectroscopic and computational techniques.

Selective Isomer Formation and Crystallization-Directed Magnetic Behavior in Nitrogen-Confused C-Scorpionate Complexes of Fe(OSCF).

The complex [Fe(L*)](OTf), , where L* = bis(3,5-dimethylpyrazol-1-yl)(3-1-pyrazole)methane, was prepared in order to compare its magnetic properties with those of the analogous parent complex, [Fe(L)](OTf), that lacks methyl groups on pyrazolyl rings and that undergoes spin crossover (SCO) from the low spin (LS) to the high spin (HS) form above room temperature. It was anticipated that this new semibulky derivative should favor the HS state and undergo SCO at a lower temperature range. During this study, six crystalline forms of were prepared by controlling the crystallization conditions.

Calix[4]arene-Based Bis(Nitric Oxide) Complexes: Synthesis, Physical Properties, and Structural Characterization.

Calix[4]arene-based molecules hold great promise as candidate sensors and storage materials for nitric oxide (NO), owing to their unprecedented binding affinity for NO. However, the structure of calix[4]arene is complicated by the availability of four possible conformers: 1,3-alternate, 1,2-alternate, cone, and partial cone (paco). Whilst complexes of NO with several of these conformers have previously been established, the 1,2-alternate conformer complex, that is, [1,2-alter⋅NO] , has not been previously reported.

Synthesis and Characterization of Anionic Lanthanide(III) Complexes with a Bidentate Sulfonylamidophosphate (SAPh) Ligand.

A series of new anionic lanthanide(III) complexes with the general formula NEt[Ln] (; H = dimethyl[(4-methylphenyl)sulfonyl]amidophosphate; Ln = La, Nd, Eu), were synthesized and characterized by IR, UV-vis, and NMR spectroscopies, the differential scanning calorimetry method, thermogravimetric and X-ray analysis, and photoluminescence measurements. Single-crystal structures of NEt[Eu] () were determined at 293 and 100 K and evidenced the phase transition. Both phases are in the monoclinic crystal system in centrosymmetric groups of the same Laue class.

Highly Selective Synthesis of Pillar[ n]arene ( n = 5, 6).

An efficient and highly selective synthetic method toward the preparation of pillar[ n]arenes ( n = 5, 6) is reported, based upon a high solvent-dependent selectivity found in the condensation reaction between 1,4-dialkyloxybenzene and paraformaldehyde, involving methanesulfonic acid as catalyst. Pillar[6]arene (P6) is obtained as the major product when using chloroform as solvent, while in dichloromethane pillar[5]arene (P5) is the dominant product. Accordingly, a series of P5 and P6 have been selectively synthesized with excellent yield.

A synthetic model of the nonheme iron-superoxo intermediate of cysteine dioxygenase.

A nonheme Fe(ii) complex (1) that models substrate-bound cysteine dioxygenase (CDO) reacts with O at -80 °C to yield a purple intermediate (2). Analysis with spectroscopic and computational methods determined that 2 features a thiolate-ligated Fe(iii) center bound to a superoxide radical, mimicking the putative structure of a key CDO intermediate.

Synthesis and evaluation of 4-cycloheptylphenols as selective Estrogen receptor-β agonists (SERBAs).

A short and efficient route to 4-(4-hydroxyphenyl)cycloheptanemethanol was developed, which resulted in the preparation of a mixture of 4 stereoisomers. The stereoisomers were separated by preparative HPLC, and two of the stereoisomers identified by X-ray crystallography. The stereoisomers, as well as a small family of 4-cycloheptylphenol derivatives, were evaluated as estrogen receptor-beta agonists.

An electron-transfer induced conformational transformation: from non-cofacial "sofa" to cofacial "boat" in cyclotetraveratrylene (CTTV) and formation of charge transfer complexes.

Electro-active polychromophoric assemblies that undergo clam-like electromechanic actuation represent an important class of organic functional materials. Here, we show that the readily available cyclotetraveratrylene (CTTV) undergoes oxidation-induced folding, consistent with interconversion from a non-cofacial "sofa" conformation to a cofacial "boat" conformer. It is found that the non-cofacial "sofa" conformer of CTTV forms stable electron donor-acceptor complexes with chloranil and DDQ.

Synthesis of Doubly Annulated m-Terphenyl-Based Molecular Tweezers and Their Charge-Transfer Complexes with DDQ as a Guest.

The synthesis of a doubly-annulated m-terphenyl-based tweezer platform has been developed, which affords ready incorporation of various pincer units from monobenzenoid to polybenzenoid electron donors. The complexation study with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) as guest has been carried out, and the crystal structure of T-Py∩DDQ reveals the sandwich-type binding mode in the solid state.

Multinuclear Cu(I) Clusters Featuring a New Triply Bridging Coordination Mode of Phosphaamidinate Ligands.

Phosphabenzamidine [mes-NH-C(Ph)═P-mes) (1) and phosphaformamidine (mes-NH-CH═P-mes) (4) ligands have been synthesized and characterized. The conjugate bases of 1 and 4 coordinate by each bridging three Cu(I) ions, forming hexa- and tetranuclear clusters Cu[mes-N═C(Ph)-P-mes]ClLi(THF) (3) and Cu[mes-N═CH-P-mes] (5), respectively. Both clusters have been fully characterized using H NMR, P NMR, and X-ray crystallography.