2-[(2-{Bis[2-(2-hy­droxy-5-nitro­benzyl­idene­amino)­eth­yl]amino}­eth­yl)imino­meth­yl]-4-nitro­phenol acetonitrile monosolvate

In the title compound, C27H27N7O9·CH3CN, the three nitro groups of the polydentate tripodal Schiff base are located approximately parallel to their respective carrier benzene rings, making dihedral angles of 3.9 (4), 5.0 (4) and 6.3 (4)°. Intra­molecular O—H⋯N hydrogen bonds between the hy­droxy O atoms and the imine N atoms, with O⋯N distances in the range 2.607 (3)–2.665 (3) Å, form nearly planar six-membered rings. In the crystal, weak inter­molecular C—H⋯O and C—H⋯N hydrogen bonds occur and several intra- and inter­molecular π–π inter­actions are present between adjacent benzene rings, with a shortest centroid–centroid distance of 3.507 (2) Å

Zwitterionic form of tris­({[5-(4-meth­oxy­phenyl­azo)salicyl­idene]amino}­eth­yl)amine

The title compound (systematic name: 2-{[2-(bis­{2-[({2-hy­droxy-5-[(4-meth­oxy­phen­yl)diazen­yl]phen­yl}methyl­idene)amino]­eth­yl}amino)­eth­yl]aza­niumylidenemeth­yl}-4-[(4-meth­oxy­phen­yl)diazen­yl]phenolate), C48H48N10O6, exists as a zwitterion in the solid state. The three arms of the tripodal mol­ecule are located close to each other and an intra­molecular hydrogen bond occurs in each arm (O—H⋯N in two arms and N—H⋯O in the zwitterionic arm). The dihedral angles between the aromatic rings in the three arms are 16.36 (14), 23.94 (14) and, for the zwitterionic arm, 37.14 (14)°. In the crystal, a weak inter­moleclar N—H⋯O hydrogen bond occurs

Design of pure heterodinuclear lanthanoid cryptate complexes

Heterolanthanide complexes are difficult to synthesize owing to the similar chemistry of the lanthanide ions. Consequently, very few purely heterolanthanide complexes have been synthesized. This is despite the fact that such complexes hold interesting optical and magnetic properties. To fine-tune these properties, it is important that one can choose complexes with any given combination of lanthanides. Herein we report a synthetic procedure which yields pure heterodinuclear lanthanide cryptates LnLn*LX(3) (X = NO(3)(−) or OTf(−)) based on the cryptand H(3)L = N[(CH(2))(2)N[double bond, length as m-dash]CH–R–CH[double bond, length as m-dash]N–(CH(2))(2)](3)N (R = m-C(6)H(2)OH-2-Me-5). In the synthesis the choice of counter ion and solvent proves crucial in controlling the Ln–Ln* composition. Choosing the optimal solvent and counter ion afford pure heterodinuclear complexes with any given combination of Gd(iii)–Lu(iii) including Y(iii). To demonstrate the versatility of the synthesis all dinuclear combinations of Y(iii), Gd(iii), Yb(iii) and Lu(iii) were synthesized resulting in 10 novel complexes of the form LnLn*L(OTf)(3) with LnLn* = YbGd 1, YbY 2, YbLu 3, YbYb 4, LuGd 5, LuY 6, LuLu 7, YGd 8, YY 9 and GdGd 10. Through the use of (1)H, (13)C NMR and mass spectrometry the heterodinuclear nature of YbGd, YbY, YbLu, LuGd, LuY and YGd was confirmed. Crystal structures of LnLn*L(NO(3))(3) reveal short Ln–Ln distances of ∼3.5 Å. Using SQUID magnetometry the exchange coupling between the lanthanide ions was found to be anti-ferromagnetic for GdGd and YbYb while ferromagnetic for YbGd

Photoreactivities of 5-Bromouracil-containing RNAs.

5-Bromouracil ((Br)U) was incorporated into three types of synthetic RNA and the products of the photoirradiated (Br)U-containing RNAs were investigated using HPLC and MS analysis. The photoirradiation of r(GCA(Br)UGC)(2) and r(CGAA(Br)UUGC)/r(GCAAUUCG) in A-form RNA produced the corresponding 2'-keto adenosine ((keto)A) product at the 5'-neighboring nucleotide, such as r(GC(keto)AUGC) and r(CGA(keto)AUUGC), respectively. The photoirradiation of r(CGCG(Br)UGCG)/r(C(m)GCAC(m)GCG) in Z-form RNA produced the 2'-keto guanosine ((keto)G) product r(CGC(keto)GUGCG), whereas almost no products were observed from the photoirradiation of r(CGCG(Br)UGCG)/r(C(m)GCAC(m)GCG) in A-form RNA. The present results indicate clearly that hydrogen (H) abstraction by the photochemically generated uracil-5-yl radical selectively occurs at the C2' position to provide a 2'-keto RNA product

NMR Observations of Interligand Interference in the Molecular Motion of Double-Stranded Dinuclear Helicates

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