Toward Synthetic Analogues of Linked Redox and Catalytic Multimetal Sites in Proteins: A Model of the Histidine−Cysteine Bridged Dicopper Array

Contiguous HisCys residues link a type 1 Cu electron-transfer site to a catalytic Cu-containing site in nitrite reductase and the multicopper oxidases. In efforts to understand the role of the linker in these multimetallic arrays and to design new catalysts, a mixed-valent dicopper complex comprising a bridging thiolate/N-donor ligand that models the CuHisCysCu motif was prepared and characterized by X-ray crystallography. Comparison of spectroscopic and cyclic voltammetry data to those of the mononuclear analogues of each portion of the complex, LCuSCPh3 and LCu(py) (L = β-diketiminate, py = pyridyl), confirmed retention of the dicopper structure in solution

Toward Synthetic Analogues of Linked Redox and Catalytic Multimetal Sites in Proteins: A Model of the Histidine−Cysteine Bridged Dicopper Array

Contiguous HisCys residues link a type 1 Cu electron-transfer site to a catalytic Cu-containing site in nitrite reductase and the multicopper oxidases. In efforts to understand the role of the linker in these multimetallic arrays and to design new catalysts, a mixed-valent dicopper complex comprising a bridging thiolate/N-donor ligand that models the CuHisCysCu motif was prepared and characterized by X-ray crystallography. Comparison of spectroscopic and cyclic voltammetry data to those of the mononuclear analogues of each portion of the complex, LCuSCPh3 and LCu(py) (L = β-diketiminate, py = pyridyl), confirmed retention of the dicopper structure in solution

Synthesis and Functionalization of BF₂‑Complexes of <i>meso</i>-Free 25-Oxasmaragdyrin

BF₂-complex of <i>meso</i>-free 25-oxasmaragdyrin is synthesized under simple reaction conditions in high yield, and the reactivity of <i>meso</i>-free carbon atom was demonstrated by carrying out functionalization followed by coupling reactions

Rhenium(I) Tricarbonyl Complexes of <i>meso</i>-Tetraaryl-21,23-diheteroporphyrins

The dithia/diselena <i>meso</i>-tetraarylporphyrins have a lesser tendency to form metal complexes because of the larger size of the heteroatom(s), which shrinks the cavity size, and the heteroatoms also have poor coordinating ability to bind metal ions. The first example of a rhenium­(I) tricarbonyl complex of 21,23-diselenaporphyrin was synthesized by treating 5,10,15,20-tetra-<i>p</i>-tolyl-21,23-diselenaporphyrin with Re­(CO)₅Cl in chlorobenzene at reflux temperature and its structural properties were compared with our earlier reported rhenium­(I) complex of tetraaryl-21,23-dithiaporphyrin. The crystal structures of rhenium­(I) complexes of diheteroporphyrins revealed that the Re^I ion binds to both the Se/S atoms and one of the N atoms of the porphyrin core along with three terminal carbonyl groups in an octahedral fashion. The rhenium­(I) complexes of 21,23-diheteroporphyrins are stabilized by a large counterion, the trichloro-bridged dirhenium­(I) ion. We also present a detailed account of the spectral and redox properties of rhenium­(I) tricarbonyl complexes of 21,23-diheteroporphyrins

Rhenium(I) Tricarbonyl Complexes of <i>meso</i>-Tetraaryl-21,23-diheteroporphyrins

The dithia/diselena <i>meso</i>-tetraarylporphyrins have a lesser tendency to form metal complexes because of the larger size of the heteroatom(s), which shrinks the cavity size, and the heteroatoms also have poor coordinating ability to bind metal ions. The first example of a rhenium­(I) tricarbonyl complex of 21,23-diselenaporphyrin was synthesized by treating 5,10,15,20-tetra-<i>p</i>-tolyl-21,23-diselenaporphyrin with Re­(CO)₅Cl in chlorobenzene at reflux temperature and its structural properties were compared with our earlier reported rhenium­(I) complex of tetraaryl-21,23-dithiaporphyrin. The crystal structures of rhenium­(I) complexes of diheteroporphyrins revealed that the Re^I ion binds to both the Se/S atoms and one of the N atoms of the porphyrin core along with three terminal carbonyl groups in an octahedral fashion. The rhenium­(I) complexes of 21,23-diheteroporphyrins are stabilized by a large counterion, the trichloro-bridged dirhenium­(I) ion. We also present a detailed account of the spectral and redox properties of rhenium­(I) tricarbonyl complexes of 21,23-diheteroporphyrins

Phosphorus Complexes of <i>meso</i>-Triaryl-25-oxasmaragdyrins

The aromatic PO₂ complexes of <i>meso</i>-triaryl-25-oxasmaragdyrins were synthesized by treating the free base 25-oxasmaragdyrins with POCl₃ in toluene/triethylamine at refluxing temperature. The complexes are stable and characterized by X-ray and different spectroscopic techniques. In these complexes, the phosphorus­(V) ion was bound to two pyrrolic nitrogen atoms of the smaragdyrin macrocycle and two oxygen atoms in tetrahedral geometry. The X-ray structure revealed that the smaragdyrin macrocycle showed significant distortion upon insertion of a PO₂ unit, and the phosphorus atom lies 1.339 Å above the mean plane defined by three <i>meso</i>-carbon atoms of the macrocycle. These complexes absorb strongly in the visible region and are 2.5 times more strongly fluorescent than free base 25-oxasmaragdyrins. The smaragdyrin macrocycle becomes electron-deficient upon complexation with a PO₂ unit because these complexes are easier to reduce but difficult to oxidize compared to free base smaragdyrins. We designed and synthesized a covalently linked BODIPY–PO₂-smaragdyrin dyad and demonstrated efficient energy transfer from the BODIPY unit to the PO₂-smaragdyrin unit

Synthesis and Functionalization of BF₂‑Complexes of <i>meso</i>-Free 25-Oxasmaragdyrin

BF₂-complex of <i>meso</i>-free 25-oxasmaragdyrin is synthesized under simple reaction conditions in high yield, and the reactivity of <i>meso</i>-free carbon atom was demonstrated by carrying out functionalization followed by coupling reactions

Stable Nonaromatic [20]Dithiaporphyrin (2.1.1.1) Macrocycles: Synthesis, Structure, Spectral, Electrochemical, and Metal Ion Sensing Studies

Stable nonaromatic [20]­dithiaporphyrin (2.1.1.1) macrocycles were synthesized in decent yields by condensing readily available butene-2,3-diyl-bisthiophene-2,5-diyl-bis­(<i>p</i>-methoxyphenylmethanol) with different <i>meso</i>-aryl dipyrromethanes under mild acid-catalyzed conditions. The [20]­dithiaporphyrin (2.1.1.1) macrocycles are the first members of the expanded porphyrin analogues of [18]­dithiaporphyrin (1.1.1.1) and consist of two pyrroles and two thiophenes connected through five <i>meso</i>-carbon bridges. The [20]­dithiaporphyrin macrocycles were confirmed by mass spectroscopy, 1D and 2D NMR spectroscopy, and X-ray crystallography. The X-ray structure revealed that the macrocycle is highly distorted and that the two thiophene rings are completely out-of-plane from the “mean-plane” defined by the dipyrromethene moiety and the two <i>meso</i>-carbons. In the absorption spectrum, the macrocycles showed one strong band at ∼420 nm and one weak band at ∼720 nm. The electrochemical studies revealed that the macrocycles are stable under redox conditions. The metal sensing studies indicated that these macrocycles have the potential to sense specific metal ions such as Hg²⁺ ions. Two covalently linked dithiahomoporphyrin–fluorophore dyads were synthesized by coupling iodo-functionalized dithiahomoporphyrin with an ethynyl-functionalized fluorophore such as boron–dipyrromethene (BODIPY) and BF₂–smaragdyrin under mild Pd(0) coupling conditions. The potential of these dyads as a fluorescent sensor for Hg²⁺ was explored, and the studies indicated that both dyads can be used as fluorescent sensors

Synthesis and Characterization of a Monocyanide-Bridged Bimetallic Iron(II) and Copper(I) Complex

Synthesis and Characterization of a Monocyanide-Bridged Bimetallic Iron(II) and Copper(I) Comple

Kinetic Study of the Insertion and Deinsertion of Carbon Dioxide into <i>f</i><i>ac</i>-(CO)₃(dppe)MnOR Derivatives

The insertion of carbon dioxide into the Mn−O bond of fac-(CO)3(dppe)MnOCH3 (1) was observed to occur instantaneously at −78 °C by in situ infrared spectroscopy. The product of carboxylation of 1, fac-(CO)3(dppe)MnOC(O)OCH3 (2), underwent decarboxylation with a first-order rate constant of 1.49 × 10-4 s-1 at 23 °C. The kinetic parameters for this process were determined by trapping the intermediate produced upon CO2 extrusion, complex 1, with COS to provide the very stable fac-(CO)3(dppe)MnSC(O)OCH3 (3) derivative. The structure of 3 was determined by single-crystal X-ray diffraction analysis, establishing the presence of the Mn−S bond