Julita Eilmes

Benzoylation of macrocyclic Jäger type Ni(II) complexes and an efficient demetalation of γ,γ'-dibenzoylated products

Abstract The reaction of [Bzo2Me4[14]hexaenato(2−)N4]Ni(II) and [Bzo2Me2Ph2[14]hexaenato(2−)N4]Ni(II) with benzoyl chloride leading to mono- and disubstituted derivatives is reported. The condition of the reliable demetalation of γ,γ′-dibenzoylated complexes by means of gaseous HCl are described. The Cu(II) complexes are synthesized from free ligands. All new compounds are characterized by elemental analysis, IR, 1H NMR and MS data.

New γ,γ′-disubstituted derivatives of macrocyclic Jäger-type Ni(II) complexes

Abstract The reaction of [Bzo 2 Me 4 [14]hexaenato(2−)N 4 ]Ni(II) and [Bzo 2 Me 2 Ph 2 [14]hexaenato(2−)N 4 ]Ni(II) with glutaryl chloride leads to new γ,γ′-disubstituted derivatives having γ,δ-unsaturated-δ-lactonic rings as substituents. The demetalation of the new complexes by means of gaseous HCl is described. The new compounds were characterized by elemental analysis, IR, 1 H NMR and MS data.

Thermodynamic fingerprints of ligand binding to human telomeric G-quadruplexes.

Thermodynamic studies of ligand binding to human telomere (ht) DNA quadruplexes, as a rule, neglect the involvement of various ht-DNA conformations in the binding process. Therefore, the thermodynamic driving forces and the mechanisms of ht-DNA G-quadruplex-ligand recognition remain poorly understood. In this work we characterize thermodynamically and structurally binding of netropsin (Net), dibenzotetraaza[14]annulene derivatives (DP77, DP78), cationic porphyrin (TMPyP4) and two bisquinolinium ligands (Phen-DC3, 360A-Br) to the ht-DNA fragment (Tel22) AGGG(TTAGGG)3 using isothermal titration calorimetry, CD and fluorescence spectroscopy, gel electrophoresis and molecular modeling. By global thermodynamic analysis of experimental data we show that the driving forces characterized by contributions of specific interactions, changes in solvation and conformation differ significantly for binding of ligands with low quadruplex selectivity over duplexes (Net, DP77, DP78, TMPyP4; KTel22 ≈ KdsDNA). These contributions are in accordance with the observed structural features (changes) and suggest that upon binding Net, DP77, DP78 and TMPyP4 select hybrid-1 and/or hybrid-2 conformation while Phen-DC3 and 360A-Br induce the transition of hybrid-1 and hybrid-2 to the structure with characteristics of antiparallel or hybrid-3 type conformation.

New unsymmetrical Schiff base Ni(II) complexes as scaffolds for dendritic and amino acid superstructures

An efficient stepwise template approach has been developed that leads to a novel Ni(II) complex of an unsymmetrical 1∶1∶1 Schiff base derived from o-phenylenediamine, benzoylacetone and salicylic aldehyde [abbreviated as salophbac Ni(II)]. The 3- and 5-hydroxysubstituted salicylic aldehydes lead to complexes containing reactive OH groups that were further employed as points of attachment for the ligand superstructures. A range of new O-substituted derivatives of salophbac Ni(II) complexes have been synthesized bearing N-protected (L)-amino acid moieties as well as poly(arylether) and poly(arylester) dendrons. New products have been characterized by means of 1H and 13C NMR, MS and IR data. The crystal structures of the 3-Boc–(L)-phenylalanyloxy, 3-Ac–(D,L)-alanyloxy and (3′,5′-dibenzyloxy)-3-benzyloxy derivatives of salophbac Ni(II) complexes have been determined. The supramolecular C–H⋯π, π⋯π interactions and hydrogen bonds are discussed on the basis of the crystallographic data.

New chiral receptors based on dibenzotetraaza(14)annulenes

Abstract Reactions of dibenzotetraaza[14]annulene Ni(II) complexes 1 and 2 with oxalyl chloride and chiral terpene alcohols ((−)menthol, (−)borneol), and the Cinchona alkaloid (quinine) afforded new mono and disubstituted derivatives bearing corresponding ester groups at the meso positions. The demetallation of di(−)menthyloxycarbonyl and di(−) bornyloxycarbonyl derivatives has been accomplished by means of gaseous HCl, leading to corresponding free bases. Single-crystal X-ray diffraction of the free ligand equipped with two (−)menthyloxycarbonyl substituents revealed a saddle-like shape of the molecule resulting in the non-equivalence of two axial coordination sites of the macrocycle. The (−) menthyloxycarbonyl substituents were found to define the ‘walls’ of a cavity on one side of the macrocyclic platform. The two menthyl rings belonging to the meso substituents appeared to be non-equivalently arranged on both propanediiminate parts of the macrocycle, relative to their phenyl and methyl substituents. The molecules of the ligand are arranged in stacking columns and form cavities in the crystal lattice. The molecules of solvent (benzene) were found to reside in these cavities. The amine protons of the central tetraaza fragment of the macrocycle are involved in two asymmetric intramolecular N−H⋯N hydrogen bonds. The 1H and 13C NMR spectra measured at room temperature, in CDCl3 solution, provided evidence of conformational non-equivalence within both meso-disubstituted propanediiminate fragments of the macrocycle. Additionally, two non-equivalent NH protons have been detected in the 1H NMR spectra of both free ligands. The new products have been characterized by elemental analyses, ESI MS, IR, 1H and 13C NMR data.

Nickel complexes of tetradentate asymmetric ligands

Abstract The crystal structures of asymmetric tetraaza and Schiff base ligands and of their nickel complexes have been determined by X-ray structural analysis: all molecules exhibit a saddle-shaped conformation which minimises the steric repulsion. The compound 5,14-dihydro-6,17-dimethyl-8,15-diphenyldibenzo[ b,i ][1,4,8,11]tetraazacyclotetradecine ( H 2 TAA ) (monoclinic, P 2 1 / a , a =14.968(2), b =20.812(2), c =17.748(2) A, β =113.60(10)°, Z =8) crystallises with two different molecules in the asymmetric unit: the two amino hydrogens in the tetraaza ring are bonded to the opposite nitrogens with an appreciable bond interaction with the nitrogen atom of the same propanediiminato fragment. The related complex NiTAA (triclinic, P 1 , a =11.556(2), b =14.043(2), c =9.656(2) A, α= 106.90(10), β =105.10(10), γ= 67.20(10)°, Z =2) shows a more extended bond delocalisation as the result of coordination to the metal centre. The Schiff base bis(benzoylacetone)- o -phenylenediamine ( H 2 DAO ) (monoclinic, P 2 1 / a , a =9.564(2), b =22.727(2), c =10.981(2) A, β =115.20(10)°, Z =4) is characterised by a very marked single-double bond alternation and the NNOO set of atoms largely deviate from planarity. Its nickel complex NiDAO (monoclinic, P 2 1 / a , a =18.151(2), b =12.188(2), c =19.362(2) A, β =96.80(10)°, Z =8) has two different molecules with very similar structural parameters in the asymmetric unit: the Ni–O and Ni–N bonds have very similar lengths and form an almost regular square plane structure.

Synthesis, reactivity, crystal and molecular structure of [5,14-dihydro-7,16-bis(2-oxo-3H-furan-5-yl)-6,8,15,17-tetramethyldibenzo[b,i][1,4,8,11]tetraazacyclotetradecinato(2-)-κ4N]nickel(II)

Abstract The reaction of the Ni(II) complex of 5,14-dihydro-6,8,15,17-tetramethyldibenzo[b,i][1,4,8,11]tetraazacyclotetradecine with succinyl dichloride leads to di- and monosubstituted derivatives bearing β,γ-unsaturated-γ-lactonic rings at the meso positions of the macrocycle. An aminolytic cleavage of these lactonic substituents gives rise to open-chain pendant groups containing the corresponding amide functions. A range of new complexes have been synthesized in this way with use of primary and secondary aliphatic and heterocyclic amines. The new products have been characterized by elemental analyses, 1H, 13C NMR, IR and ESI-MS spectral data. Single crystal X-ray studies revealed that the saddle-shaped molecules of [5,14-dihydro-7,16-bis(2-oxo-3H-furan-5-yl)-6,8,15,17-tetramethyldibenzo[b,i][1,4,8,11]tetraazacyclotetradecinato(2-)-κ4N]nickel(II) act as receptors with molecules of toluene forming 1:1 supramolecular complexes.

Reactivity of the macrocyclic complex [Ni(C22H22N4)] toward cyanogen

Abstract The macrocyclic complex (2,3:9,10-dibenzo- 5,7,1 2,14-tetramethyl-1,4,8,11-tetraazacyclotetradeca- 2,4,6,9,11,13-hexaenato(2−)- k4N)nickel(II), [Ni(Bzo2Me4[14]hexaenatoN4)] reacts with cyanogen under mild conditions to give addition-insertion to the methine CH group. The two resulting complexes are characterized by one or two cyanoimino methyl C(NH)CN substituents, from which HCN can be easily released to give the corresponding cyano derivatives. The mono cyano complex [Ni(Bzo2(CN)Me4 [14]hexaenatoN4)] crystallizes in the monoclinic system (space group P21/n) and has a saddle-shaped structure, in which the benzene and β-diiminato groups are tilted in opposite directions, with respect to the plane defined by the four nitrogen and the nickel atoms (CN bond distance 1.141(14) A).

Dibenzotetraaza[14]annulene–adenine conjugate recognizes complementary poly dT among ss-DNA/ss-RNA sequences

Among three novel DBTAA derivatives only the DBTAA-propyl-adenine conjugate showed recognition of the consecutive oligo dT sequence by increased affinity and specific induced chirooptical response in comparison to other single stranded RNA and DNA; whereby of particular importance is the up until now unique efficient differentiation between dT and rU. At variance, its close analogue DBTAA-hexyl-adenine did not reveal any selectivity between ss-DNA/RNA pointing out the important role of steric factors (linker length); moreover non-selectivity of the reference compound (, lacking adenine) stressed the importance of adenine interactions in the selectivity.

A new synthetic strategy towards dibenzotetraaza[14]annulenes bearing alkoxycarbonyl and aryloxycarbonyl pendant substituents

Abstract A new and efficient procedure has been developed for introducing alkoxycarbonyl and aryloxycarbonyl groups at the meso positions of the dibenzotetraaza[14]annulene Ni(II) complex. Ester substituents have been generated in one-pot, two-step procedure involving successive reactions with oxalyl dichloride (or phosgene) and appropriate HO-function-containing substrates. A range of new Ni(II) complexes equipped with ester groups derived from various alcohols and phenols have been prepared. The method proved to be applicable to the alcohols and phenols bearing other functional groups e.g. carbonyl (formyl, keto), nitro and azo groups, as well as double and triple bonds (allyl, propargyl). Highly lipophilic COOR substituents (where R = n -alkyl (C 14 –C 18 ), cholesteryl and DL-α-tocopheryl) have been also incorporated into the macrocycle. The new products have been characterized by elemental analysis, ESI and MALDI-TOF MS, IR, 1 H and 13 C NMR data.