Studies of crown ether complexes aryldiazonium ion complexes

DNMR studies show that for complexation of aryldiazonium salts 21-crown-7 is the preferred host.     

DNA-protein complexes

Sera of patients with different types of leukemia and acquired immune deficiency syndrome (AIDS) have been examined for the presence of the anti-DNA antibodies. DNA-hydrolyzing activity of antibodies was detected in the sera of patients with chronic lymphoid leukemia (CLL), pre-B-cell acute lymphoid leukemia (pre-B-All), acute myeloleukosis (AML), and AIDS in stages III and IV of the disease. In immunofluorescence tests, the DNA-hydrolyzing antibodies reacted preferentially with proliferating cell nuclei compared with resting cells. A 35-kDa factor was identified as the target for the DNA antibodies in the cell nuclei. The DNA-hydrolyzing antibody fraction from the serum of an AIDS patient crossreacted with HIV I virus proteins gp160, gp120, and p65.     

Formation of cis-enediyne complexes from rhenium alkynylcarbene complexes

Dimerization of the alkynylcarbene complex Cp(CO)(2)Re=C(Tol)C(triple bond)CCH(3) (8) occurs at 100 degrees C to give a 1.2:1 mixture of enediyne complexes [Cp(CO)(2)Re](2)[eta(2),eta(2)-TolC(triple bond)CC(CH(3))=C(CH(3))C(triple bond)CTol] (10-Eand 10-Z), showing no intrinsic bias toward trans-enediyne complexes. The cyclopropyl-substituted alkynylcarbene complex Cp(CO)(2)Re=C(Tol)C(triple bond)CC(3)H(5) (11) dimerizes at 120 degrees C to give a 5:1 ratio of enediyne complexes [Cp(CO)(2)Re](2)[eta(2),eta(2)-TolC(triple bond)C(C(3)H(5))C=C(C(3)H(5))C(triple bond)CTol] (12-E and 12-Z); no ring expansion product was observed. This suggests that if intermediate A formed by a [1,1.5] Re shift and having carbene character at the remote alkynyl carbon is involved, then interaction of the neighboring Re with the carbene center greatly diminishes the carbene character as compared with that of free cyclopropyl carbenes. The tethered bis-(alkynylcarbene) complex Cp(CO)(2)Re=C(Tol)C(triple bond)CCH(2)CH(2)CH(2)C(triple bond)CC(Tol)= Re(CO)(2)Cp (13) dimerizes rapidly at 12 degrees C to give the cyclic cis-enediyne complex [Cp(CO)(2)Re](2)[eta(2),eta(2)-TolC(triple bond)CC(CH(2)CH(2)CH(2))=CC(triple bond)CTol] (15). Attempted synthesis of the 1,8-disubstituted naphthalene derivative 1,8-[Cp(CO)(2)Re=C(Tol)C(triple bond)C](2)C(10)H(6) (16), in which the alkynylcarbene units are constrained to a parallel geometry, leads to dimerization to [Cp(CO)(2)Re](2)(eta(2),eta(2)-1,2-(tolylethynyl)acenaphthylene] (17). The very rapid dimerizations of both 13 and 16 provide compelling evidence against mechanisms involving cyclopropene intermediates. A mechanism is proposed which involves rate-determining addition of the carbene center of A to the remote alkynyl carbon of a second alkynylcarbene complex to generate vinyl carbene intermediate C, and rearrangement of C to the enediyne complex by a [1,1.5] Re shift.     

Penta-arylcyclopentadienyl complexes

This review covers the coordination and general chemistry of the 1,2,3,4,5-penta-arylcyclopentadiene system, as anion, C₅Ar₅^?, radical, C₅Ar₅, and cation, C₅Ar₅⁺, as well as the neutral diene, C₅Ar₅H, and its derivatives. The structural rigidity and steric saturation offered by the penta-arylcyclopentadienyl ligand give rise to definite structural and geometric properties in its complexes that distinguish its chemistry from that of the parent cyclopentadiene.     

Arene-manganese complexes

Direct reaction between arene and the perchlorate Mn(CO)₅OClO₃ provides a simple, rapid and uncatalysed route to the salts [(arene)Mn(CO)₃]⁺. Hydrolysis of [(C₆H₅F)Mn(CO)₃]⁺ yields the corresponding phenol complex which is readily deprotonated to the weakly basic oxocyclohexadienyl complex, C₆H₅O)Mn(CO)₃.     

Helical metallohost-guest complexes via site-selective transmetalation of homotrinuclear complexes

We have designed a new type of bis(N2O2) chelate ligand that affords a C-shaped O6 site on the metalation of the N2O2 sites. UV-vis and 1H NMR titration clearly showed that the complexation between H4L and zinc(II) acetate affords 1:3 complex [LZn3]2+ via a highly cooperative process. Although the O6-recognition site of the dinuclear metallohost [LZn2] is filled with the additional Zn2+, the O6 site can bind a guest ion with concomitant release of the initially bound Zn2+. The novel recognition process "guest exchange" took place quantitatively when rare earth metals were used as a guest. In the case of alkaline earth metals, selectivity of Ca2+ > Sr2+ > Ba2+ > Mg2+ was observed. On the other hand, the transmetalation did not take place at all when alkali metals were used for the guest. Accordingly, the trinuclear complex [LZn3]2+ is excellent in discriminating charge of the guest ions. The metallohost-guest complexes thus obtained have a helical structure, and the radius d and winding angle theta of the helix depend on the size of the guest. The La3+ complex has the smallest theta (288 degrees), and the Sc3+ complex has the largest theta (345 degrees). Because the radius and winding angles of helices are tunable by changing the guest ion, the helical metallohost-guest complexes are regarded as a molecular spring or coil. Consequently, site-specific metal exchange of trinuclear complex [LZn3]2+ described here will be utilized for highly selective ion recognition, site-selective synthesis of (3d)2(4f) trimetallic complexes, and construction of "tunable" metallohelicenes.     

Xanthan gum-gelatin complexes

Gelatin (G) and xanthan gum (X) formed complexes either on bringing their blends to pH 2.3 or carrying out the electrode process in aqueous blends of X and G at pHs from 9 to 11. X carboxylic groups and G peptide moieties were involved in the interactions between the partners. Also non-coulombic interactions with involvement of NH and OH groups, as well as hydrophobic interactions were involved, as proved by FTIR and thermal analyses, respectively. The reaction yield declined with increase of concentration of G in the blends. Simultaneously, the thermal stability of the complexes slightly increased with increase in G content in the blend. The latter increased with its concentration in the reaction mixture. Slow formation by electrosynthesis provided more an organised matrix.     

Dithiocarbene complexes derived from CS2 -bridged dinuclear complexes

Stable dithiocarbene complexes {CP(CO)₂FeC(SCH₃)[SML_n]}⁺ (ML_n = Re(CO)₅, Fe(CO)₂Cp) are formed when monodentate ferrodithiocarboxylate—metal complexes Cp(CO)₂FeC(S)[SM′L_n] (Cp  η⁵ -C₅H₅) are treated with CH₃SO₃CF₃.