Antioxidant activity and photochromic properties of 2,6-bis (2,4- dihydroxybenzylidene) cyclohexanone

Xanthylium derivatives have attracted considerable interest due to their potential health effects and replacement of synthetic pigments. Moreover, these type of compounds exhibit versatile photochromic properties by switching from a variety of colors when submitted to external stimuli (light, temperature, pH). Generally, all these compounds hold the same xanthylium core and follow the same pH-dependent network of reversible chemical reactions as structurally related families such as flavylium [1-4]. In the present study we focused the attention on the isolation and characterisation of of the species involved in the network of chemical reactions of 2,6-bis(2,4- dihydroxybenzylidene)cyclohexanone. The pH-dependent photochromic behavior of the xanthylium derivative has been investigated. In order to identify the species, the NMR spectra were recorded in acidic and basic media. The antioxidant activity was also determined using DPPH assay [5]. The IC50 values of radical scavenging activity for DPPH were found to be 133.68 μg/mL

Structural characterization of 3d metal complexes containing an unconventional schiff base ligand

The design of appropriated organic ligands capable of binding metal ions provides a targeted entry to new materials with distinct structural and physicochemical properties. A representative family of such ligands includes Schiff bases. Here, we report new mono, diand polynuclear materials [Co(L)]3(ClO4)3·4H2O (1), [Zn2(L)(CH3COO)2] (2) and [Cu3(L)2(µ3 -ClO4)0.66](ClO4)1.33·1.33CHCl3 (3) containing N,N’-bis[(2- hydroxybenzilideneamino)-propyl]-piperazine (H2L) Schiff base as hexadentate ligand (Figure 1). The X-ray crystallography of the complexes reveal a retaining of the original chair piperazine conformation from the free ligand in the complex 2 and a changing into a boat conformation in the complexes 1 and 3. Moreover, in the respective complexes a different coordination number as 6 (1), 5 (2) and 4 and 5 (3) was observed upon coordination of the free ligand to Co(III), Zn(II) and Cu(II) ions. The modulatory property of H2L is reflected upon the molecular assembly and coordination mode of the isolable species

Homoleptic and heteroleptic pt(II) complexes with potential biological activity

Metal complexes used as pharmaceuticals have received great attention because of their potential biological activity. The chemistry of platinum(II) complexes has been widely developed since the cytostatic activity of cis-diaminodichloroplatinum(II) (cisplatin) has been discovered [1]. Moreover, transition metal complexes containing planar polycyclic aromatic systems intercalate between the stacked base pairs of DNA. The biological activity of both cis- and trans-diamine Pt(II) complexes is dramatically enhanced by the presence of aromatic intercalator ligands, due to the influence on both kinetics and thermodynamics of DNA binding [2,3]. The chemistry of Pt(II) complexes is highly versatile, permitting the design and synthesis of a large variety of different structures. By ‘smart’ molecular engineering, new structures are programmed and obtained continuously, in an attempt to overcome the drawbacks of the cisplatinum like tumor resistance, or to lessening unpredictable and severe nephrotoxicity and/or providing oral bioavailability. Herein, new Pt(II) complexes as DNA intercalators were synthesized and characterized aiming to follow their structure – activity relationships. The synthesis and characterization of the complexes will be presented

Synthesis and structural characterization of dimeric and polymeric cooper(II) complexes with schiff base as ligand

Polynuclear coordination compounds derived from multidentate Schiff base ligands are a source of new materials with applications in catalysis [1], optoelectronic materials [2], and environmental applications [3]. In extension of our previous studies [4]on polynuclear materials, we report the crystal structures and spectroscopic properties ofdimeric and polymeric copper(II) complexeswith hexadentate Schiff base N,N’-bis[(2- hydroxybenzilideneamino)-propyl]-piperazine (H2L) as ligand. Reaction of Cu(ClO4)2 hexahydrate with H2L in the presence of triethylamine affords a polymeric structure [Cu3L2(μ3-ClO4)0.66](ClO4)1.33·1.33CHCl3(1) in which the perchlorate anion acts as a tridentate ligand in a μ3-manner binding three Cu3L2 units. When NaN3 was added to the above mentioned reaction mixturea new dimeric assembly[Cu6(C24H30N4O2)4(N3)2][ClO4]2 (2) was obtained in which two azide groups bridge two Cu3L2 unitsin an end-to-end fashion. The same dimeric structure was obtained when the polymer 1 was treated with NaN3