New boronates prepared from 2,4-pentanedione derived ligands of the NO2 and N2O2 type – comparison to the complexes obtained from the corresponding salicylaldehyde derivatives

Synthesis and properties of novel polyurethanes based on amino ethers of boric acid for gas separation membranes

Herein we present the structural and mechanical properties of polyurethanes synthesized from amino ethers of boric acid for gas separation.

Lanthanide Complexes of Substituted β-Diketone Hydrazone Derivatives: Synthesis, Characterization, and Biological Activities

A series of β-diketone hydrazone derivatives have been synthesized through condensation of β-diketone with aromatic aldehydes followed by reaction with phenylhydrazine. The structure of the ligands and intermediates are well defined through elemental and spectroscopic analyses. These hydrazones are potential ligands toward lanthanide metal ions. New complexes of trivalent Scandium, Yttrium, Lanthanum, and Cerium have been synthesized. The composition of these complexes is discussed on the basis of elemental analyses, IR, magnetic moments, and thermal analyses. The prepared complexes were screened for antibacterial and antifungal properties and have exhibited potential activity.

2,4,6-Tris-(4-fluoro-phen-yl)-2-(1-pyrid-yl)-boroxine

Crystals of the title compound, C₂₃H₁₇B₃F₃NO₃, were obtained unintentionally by slow evaporation of a chloro­form solution of the preformed boroxine–pyridine adduct. The mol­ecule contains three fluoro-substituted benzene rings, each bonded to one of the three B atoms of a six-membered boroxine ring. A pyridyl ring is also bound to one of the B atoms through a Lewis acid–base inter­action. The binding of the pyridyl substituent causes the otherwise planar boroxine ring to twist, resulting in a maximum torsion angle within the ring of 17.6 (2)°.

Salicylaldimine dimers derived from 2-H2NC6H4Bpin (pin = 1,2-O2C2Me4)

Condensation of salicylaldehyde (2-HOC6H4C(O)H) with 2-H2NC6H4Bpin (pin = 1,2-O2C2Me4) afforded the macrocyclic dimer 1 with an OBOBO structural unit. Similar reactivity with substituted salicylaldehyde derivatives gave the corresponding Schiff bases 2–6. Crystals of 1 were triclinic, space group P-1, a = 9.7915(4) Å, b = 10.8569(5) Å, c = 12.8445(6) Å, α = 102.067(1)°, β = 96.011(1)°, γ = 90.458(1)°, Z = 2. All new compounds have been tested for their antifungal activity against Aspergillus niger and Aspergillus flavus.Key words: antifungal, boron, dehydration, heterocycles, Schiff bases.

Late metal salicylaldimine complexes derived from 5-aminosalicylic acid — Molecular structure of a zwitterionic mono Schiff base zinc complex

Condensation of salicylaldehyde (2-HOC6H4C(O)H) with 5-aminosalicylic acid (5-H2NC6H3-2-(OH)-CO2H) afforded the Schiff base 2-HOC6H4C(H)=NC6H3-2-(OH)-5-CO2H (a). Similar reactivity with 5-bromosalicylaldehyde was also observed to give 5-Br-2-HOC6H3C(H)=NC6H3-2-(OH)-5-CO2H (b). Reaction of these salicylaldehydes with Pd(II), Cu(II), and Zn(II) salts gave the corresponding bis(N-arylsalicylaldiminato)metal complexes (M = Pd (1), Cu (2), Zn (3)). The molecular structure of the Schiff base compound a has been confirmed by an X-ray diffraction study. Crystals of a were monoclinic, space group P2(1)/c, a = 7.0164(7) Å, b = 11.0088(11) Å, c = 14.8980(15) Å, β = 102.917(2)°, Z = 4. The molecular structure of a novel zwitterionic conformer of 3a was also characterized by an X-ray diffraction study. Crystals of 4 were monoclinic, space group P2(1)/c, a = 9.5284(5) Å, b = 19.5335(11) Å, c = 8.6508(5) Å, β = 90.596(1)°, Z = 4. All new compounds have been tested for their antifungal activity against Aspergillus niger and Aspergillus flavus. Key words: 5-aminosalicylic acid (5-ASA), antifungal, copper, palladium, salicylaldimines, Schiff base, zinc.

Preparation and Structural Characterization of Three Types of Homo- and Heterotrinuclear Boron Complexes: Salen{[B−O−B][O2BOH]}, Salen{[B−O−B][O2BPh]}, and Salen{[B−O−B][O2P(O)Ph]}

Three types of homo- and heterotrinuclear boron complexes have been obtained in moderate to good yields from reactions of salen-type ligands with boric acid and combinations of boric acid with phenylboronic and phenylphosphonic acid. The products are air-stable and have relatively high melting points (>290 degrees C) but are poorly soluble or insoluble in common organic solvents. They have been characterized as far as possible by elemental analysis, mass spectrometry, IR, (1)H, (11)B, and (31)P NMR spectroscopy, and X-ray crystallography. Furthermore, theoretical calculations have been performed for representative examples to permit a complete comparison of the different structure types. A detailed analysis of the molecular structures showed that the complexes are constructed around a central B(3)O(3) or B(2)PO(3) ring. The salen ligands are attached to two boron atoms of these rings, which have therefore tetrahedral coordination geometries. The complexes contain seven- and eight-membered heterocycles of the B(2)C(n)ON(2) (n = 2, 3) type with chair or twisted-chair and boat-chair or chair-chair conformations, respectively. In the homotrinuclear complexes one of the three boron atoms is three-coordinate and can therefore still act as Lewis acid, thus making these products interesting for catalytic applications, e.g. in asymmetric synthesis. Depending on the substitutents attached to the boron atoms, these complexes show a relationship with either trimetaboric acid, boroxine, or the tetraborate dianion found in Borax.