Peter Gantzel

A Photoluminescent Copper(I) Complex with an Exceptionally High CuII/CuI Redox Potential: [Cu(bfp)2]+ (bfp=2,9-bis(trifluoromethyl)-1,10-phenanthroline)

Unprecedented stabilization of the copper(I) oxidation state is demonstrated for the complex cation [Cu(bfp)2 ]+ (1) due to the steric and electronic effects of the CF3 groups (E1/2 (CuII /CuI )=+1.55 V vs. SCE). The redox existence range of the copper(I) species is remarkably high at 2.77 V. It is emissive in solution at room temperature and shows great potential as a photocatalyst; in the excited state it is a very potent photooxidant.

Long CC single bonds in anthracene dimers: The structure of bi(anthracene-9,10-dimethylene) photodimer is redetermined

Abstract Ab Initio HF and DF Theory computations are performed on anthracene dimers 1–3 Crystal structures are redetermined at low temperature for 2 and 3. The 1.77 A central bond length previously reported for 3 is shown to be only 1.648 A. Through-bond coupling as a primary cause of bond lengthening in 1–3 is questioned.

ZIGZAG CHAIN OF HEPTA-COORDINATE MANGANESE COMPLEXES

Abstract The preparation of the polymeric chain complex, }[Mn(bic)(H2O)]2 · 2Br · 2H2O){n (2) is reported. Characterization is made by single X-ray structure, IR and magnetochemistry data. Each seven-coordinate manganese ion has a slightly distorted pentagonal bipyramidal coordination geometry. Bicine is a hexadentate ligand using one nitrogen, three oxygen and one μ2-oxygen atom from the carboxylate group to coordinate to two MnII ions. The two hydroxyl groups are not deprotonated, and the μ2-oxygen atom of the carboxylate moiety of the bic− ligand is a bridge leading to a polymeric chain. One water molecule coordinates to the MnII ion, and also forms a strong hydrogen bond with other non-coordinated water molecules. Both non-coordinated water and counter Br− ion are located between the zigzag chains. Weak pairwise antiferromagnetic exchange interactions (J = −1.42 cm−1) are found within the chain complex due to antiparallel geometry orientations of neighboring MnII centers.

Chiral sulfur diphosphazanes derived from S-(Ph2P)2N(CHMePh) and its rhodium(I), (III) and iridium(III) complexes. Crystal structures of Ph2P(S)N(CHMePh)PPh2, {Ph2P(S)}2N(CHMePh) and [(Cp*)MCl{η2-P, S-Ph2PNHP(S)Ph2}]BF4, Cp* = η5-C5Me5; M = Rh, Ir

Abstract The reaction of S-(Ph 2 P) 2 N(CHMePh) with sulfur (1:1 molar ratio) in diethyl ether solution leads to S-Ph 2 P(S)N(CHMePh)PPh 2 ( 1 ). The disulphide S-{Ph 2 P(S)} 2 N(CHMePh) ( 2 ), was obtained when the reaction was carried out in tetrahydrofuran with an excess of sulfur (1:5 molar ratio). 1 reacts with the solvated rhodium (I) complex [Rh(cod)S x ]BF 4 to afford the cationic complex [Rh(cod){η 2 -S,P-Ph 2 P(S)N(CHMePh)PPh 2 }]BF 4 ( 3 ). However, when the above reaction was carried out with 2 , cleavage of the CN bond of the ligand occurred, to yield the complex [Rh(cod)(η 2 -S,S-{Ph 2 P(S)} 2 NH)]BF 4 ( 4 ). Reactions of 1 with the fragments of Rh (III) and Ir (III) [Cp*MClS x ]BF 4 lead to cleavage of the CN bond of the ligand yielding cationic complexes, [(Cp*)MCl{η 2 -P,S-Ph 2 PNHP(S)Ph 2 }]BF 4 (M=Rh, 5 ; Ir, 6 ]. Crystal structures of 1 , 2 , 5 and 6 have been determined by X-ray diffraction methods. Compounds 1 and 2 crystallize in the same space group P 2(1)2(1)2(1). The molecular structure of 1 shows a nearly trigonal planar nitrogen atom bound to two different phosphorus atoms and to the chiral carbon atom. Compound 2 acquires a twisted conformation with the two sulfur atoms adopting mutually trans positions with respect to the PNP backbone.

Partial bond localization in the crystal structure of trisbicyclo[2.2.1]heptabenzene and its effect on Cr-arene dynamics

Abstract Trisbicyclo[2.2.1]heptabenzene 3 crystallizes in space group P2 1 /c with cell dimensions a = 5.992 A, b = 17.288 A, c = 14.843 A. Mild bond localization is seen in the benzene ring (d exo(ave) = 1.379A; d endo(ave) = 1.417A) and the annelation angle C (ar) C (ar) C (CH) is constricted to 106.5°. The structure supports a bicyclic strain effect on the bond localization in benzenoid aromatics.

Tilted amides in amino acid and peptide derivatives

BACKGROUND Amide bonds in peptides and proteins typically adopt planar cis or trans conformations. Conversions between cis and trans amide conformations are necessary for protein folding and for many other processes, but are difficult to achieve since they involve disruption of the planarity of the bond. As a first step to understanding cis-trans isomerization, we set out to synthesize and characterize peptides that mimic the tilted or twisted amide structures that are postulated to form the intermediate states in this process. RESULTS We have synthesized a model amino acid and four dipeptide derivatives containing a methyl-substituted aziridine residue. Single crystals of phenacyl (2R, 3R)-benzyloxycarbonyl-3-methyl-2-aziridinecarboxylate and phenacyl (2R, 3R)-acetyl-glycyl-3-methyl-2-aziridine-carboxylate were obtained. Using X-ray diffraction analysis, we determined that the amide nitrogens of the aziridine rings have tetrahedral sp3-like geometry with tilt angles in the range of 37-38 degrees. The 13C-NMR spectra indicate that the amide carbonyl is dramatically shifted downfield as a consequence of the tilt. CONCLUSIONS In peptides containing a substituted aziridine ring, the orbitals of the amide nitrogen are constrained into a tilted configuration. These peptides may mimic the transition state between cis and trans amide conformations. This technique thus provides a novel strategy for the study of isomerization and other biorecognition processes.

Sesquiterpenes from Omphalotus illudens

Three sesquiterpenes, illudosone hemiacetal (1a), isoomphadione (2) and illudiolone (3) were isolated from the liquid culture extract of Omphalotus illudens. Their structures were elucidated by spectroscopic techniques as well as by X-ray crystallographic analysis.

Lanthanide–tungsten heterobimetallic complexes viaσ-bond metathesis

Reactions of [{Ln(C5Me5)2H}2](Ln = Y, Sm) with [W(C5H5)2H2] afford the σ-bond metathesis products [(C5Me5)2Ln(µ-η1, η5-C5H4)(µ-H)2W(C5H5)], via dehydrocoupling between the Ln–H bond and the C–H (but not the weaker W–H) bond of [W(C5H5)2H2].

Bis(triisopropylsilyl)-o-phenylenediamido complexes of tantalum. X-ray structure of (η5-C5Me5)[o-C6H4(NSiPri3)2]TaCl2

Abstract The new mixed-ligand complexes CP ∗ [o- C 6 H 4 ( NSiPr i 3 ) 2 ] TaCl 2 (1 and Cp ∗ [o- C 6 H 4 ( NSiPr i 3 ) 2 ] TaMe 2 (2) have been prepared and characterized. In complex 1 the diamide ligand is coordinated in an η4-fashion via donation of electron density from the phenylene ring to the metal. Preliminary reactivity studies for these complexes are described.

1,6,7,10-Tetramethylfluoranthene: Synthesis and structure of a twisted polynuclear aromatic hydrocarbon.

The structure and synthesis of the overcrowded polynuclear aromatic 1, 6, 7, 10-tetramethylfluoranthene, 1 , is presented. The structures of 1 and 11 have been determined by X-ray diffraction to be twisted into conformations of approximately C 2 symmetry due to the buttressing of the flanking methyl groups. Semi-empirical calculations (AM1) on 1 find two minima, twist and fold; the twist is of lower energy. The energy for enantiomerization of 1 is set at below 7.0 kcal/mol by variable temperature NMR. Computations predict a likely path to account for the ribbon twist.