Speciation study of the anti-inflammatory drug tenoxicam (Htenox) with Cu(II): X-ray crystal structure of [Cu(tenox)(2)(py)(2)].EtOH.
A speciation study was carried out in aqueous solution of the anti-inflammatory drug tenoxicam (Htenox), under quasi-physiological conditions (temperature of 37 degrees C and ionic strength 0.15 M NaCl) in order to determine the acidity constants from spectrophotometric studies, the pK(a) values found being pK(1)=1.143+/-0.008 and pK(2)=4.970+/-0.004. Subsequently, the spectrophotometrical speciation of the different complexes of Cu(II) with the drug was performed under the same conditions of temperature and ionic strength, observing the formation of Cu(Htenox)(2)(2+) with log beta(212)=20.05+/-0.01, Cu(tenox)(2) with log beta(012)=13.6+/-0.1, Cu(Htenox)(2+) with log beta(111)=10.52+/-0.08, as well as Cu(tenox)(+) with log beta(011)=7.0+/-0.2, all of them in solution, and solid species Cu(tenox)(2)(s) with an estimated value of log beta(012)(s) approximately 18.7. The crystalline structure of the complex [Cu(tenox)(2)(py)(2)]. EtOH, was also determined, and it was observed that tenoxicam employs the oxygen of the amide group and the pyridyl nitrogen to bond to the cation.
Moya-Hernández
M R
MR
Universidad Autónoma Metropolitana-Iztapalapa, Depto Química, Apdo Postal 55-534-9340, D F, México, Mexico.
Mederos
A
A
Domínguez
S
S
Orlandini
A
A
Ghilardi
C A
CA
Cecconi
F
F
González-Vergara
E
E
Rojas-Hernández
A
A
D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000737:chemistry* / Q000378:metabolism; D003300:Copper / Q000737:chemistry* / Q000378:metabolism; D018360:Crystallography, X-Ray; D004578:Electron Spin Resonance Spectroscopy; D000431:Ethanol / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D008958:Models, Molecular; D009942:Organometallic Compounds / Q000737:chemistry / Q000378:metabolism; D010894:Piroxicam / Q000031:analogs & derivatives* / Q000737:chemistry* / Q000378:metabolism; D013056:Spectrophotometry, Ultraviolet
D000894:Anti-Inflammatory Agents, Non-Steroidal; D009942:Organometallic Compounds; D010894:Piroxicam; D000431:Ethanol; D003300:Copper; C032801:tenoxicam