No abstract

Solutions of C60, C60O, or C70 and metal complexes of octaethylporphyrin (OEPH2) yield crystals that contain both the fullerene and the porphyrin. The structures of C60·2CoII(OEP)·CHCl3, C60·2ZnII(OEP)·CHCl3, and C60O·2CoII(OEP)·CHCl3 are isomorphous and contain an ordered C60 cage surrounded by two MII(OEP) units. Although there is no covalent bond between the fullerene and porphyrin components, the separation between these units is shorter than normal van der Waals contact. Crystals of C70·CoII(OEP)·C6H6·CHCl3, C70·NiII(OEP)·C6H6·CHCl3, and C70·CuII(OEP)·C6H6·CHCl3 are also isomorphous with an ordered fullerene, but have only one porphyrin/fullerene contact. Crystalline C60·ClFeIII(OEP)·CHCl3 lacks the close face-to-face porphyrin/porphyrin contact that is common to all of the other structures reported here but retains the intimate contact between the porphyrin and the fullerene. In (C120O)·CoII(OEP)·0.6C6H6·0.4CHCl3 the fullerene dimer is enclosed by two CoII(OEP) moieties. Unfortunately disorder in the fullerene portion obscures details of the geometry of the bridging region between the fullerenes.

Unnatural amino acid 2 (5-HO2CCONH-2-MeO-C6H3-CONHNH2) duplicates the hydrogen-bonding functionality of one edge of a tripeptide β-strand. It is composed of hydrazine, 5-amino-2-methoxybenzoic acid, and oxalic acid groups and is designated by the three-letter abbreviation “Hao” to reflect these three components. The 2,7-di-tert-butylfluorenylmethyloxycarbonyl (Fmoc*)- and tert-butyloxycarbonyl (Boc)-protected derivatives of Hao are prepared efficiently and in high yield by the condensation of suitably protected derivatives of hydrazine, 5-amino-2-methoxybenzoic acid, and oxalic acid. Fmoc*-Hao and Boc-Hao behave like typical Fmoc- and Boc-protected amino acids and can be incorporated into peptides by standard solid- and solution-phase peptide synthesis techniques using carbodiimide coupling agents. Hao-containing peptide 9 (i-PrCO-Phe-Hao-Val-NHBu) forms a β-sheetlike hydrogen-bonded dimer in CDCl3 and CD3OD−CDCl3 solutions. Peptides containing Hao and natural amino acids display hydrogen-bonding surfaces that are complementary to the hydrogen-bonding edges of protein β-sheets.

Dichloro(pentamethylcyclopentadienyl)rhodium(III) dimer, [{(η 5 -C 5 Me 5 )RhCl 2 } 2 ] (1), reacts with diphenylvinylphosphine to produce [(η 5 -C 5 Me 5 )Rh{CH 2 CHP(C 6 H 5 ) 2 }Cl 2 ] (2) and [(η 5 -In acetonitrile, compound 1 undergoes a base-promoted hydroalkylation reaction with potassium tert-butoxide and diphenylvinylphosphine to produce [{η 5 . Compounds 4a-c and 5a-c contain chelating 1,3-and 1,2-bis-((diphenylphosphino)propyl)trimethylcyclopentadienide ligands. Compounds 2 and 3 are precursors on the pathway toward formation of 4a and 5a. Compound 1 reacts with allyldiphenylphosphine to produce [(η 5 -C 5 Me 5 )Rh{CH 2 CHCH 2 P(C 6 H 5 ) 2 }Cl 2 ] (6) and [(η 5 -C 5 -Me 5 )Rh{CH 2 CHCH 2 P(C 6 H 5 ) 2 } 2 Cl]X (7, X ) Cl -(a), PF 6 -(b)). In acetonitrile, compound 1 reacts with allyldiphenylphosphine in the presence of potassium tert-butoxide to produce a complex mixture of products that may contain hydroalkylation adducts. Dichloro-{(trifluoromethyl)tetramethylcyclopentadienyl}rhodium(III) dimer, [{(η 5 -C 5 Me 4 CF 3 )RhCl 2 } 2 ] (8), reacts with diphenylvinylphosphine to produce [(η 5 -C 5 Me 4 CF 3 )Rh{CH 2 CHP(C 6 H 5 ) 2 }Cl 2 ] (9), however the bis(phosphine) analog cannot be isolated or characterized. In refluxing ethanol, compound 8 reacts with diphenylvinylphosphine in the absence of potassium tertbutoxide to undergo hydroalkylation accompanied by conversion of the CF 3 group into a carboethoxy functionality producing [{η 5 -C 5 (CO 2 Et)Me 3 -2-[CH 2 CH 2 CH 2 P(C 6 H 5 ) 2 ]}RhCl 2 ] (10). Complexes 3b, 7b, and 10 were characterized by single-crystal X-ray crystallography.