Hector Saavedra | Universidad Autónoma de Chiapas (original) (raw)
Papers by Hector Saavedra
![Research paper thumbnail of Solvent dependent switching of 3MLLCT and 1IL luminescent states in [ClRe(CO)3(bathocuproinedisulfonate)]2-: spectroscopic and computational study](https://a.academia-assets.com/images/blank-paper.jpg)
](The journal of physical chemistry. A, Jan 16, 2014
Steady state and time-resolved luminescence experiments and calorimetric studies, as well as time... more Steady state and time-resolved luminescence experiments and calorimetric studies, as well as time-dependent density functional theory calculations performed on [ClRe(CO)(3)(Bathocuproinedisulfonate)](2-), show that the photophysical properties of the Re(I) anionic complex are determined by the balance between intraligand ((1)IL) and metal-ligand-to-ligand charge transfer ((3)MLLCT) excited states. In organic solvents, (3)MLLCT states prevail and the usual expected behavior is observed: bathochromic shift of the emission maximum, a reduced luminescence quantum yield and the shortening of the excited-state lifetime upon increasing the polarity of the solvent. In addition, singlet oxygen ((1)O2) is generated with high quantum yields (Φ(Δ) ≈ 0.5 in CH(3)CN) due to the quenching of the (3)MLLCT luminescence by (3)O2. The total quenching rate constant of triplet state by oxygen, k(q), reach values between 2.2 and 2.4 × 10(9) M(-1) s(-1) for the organic solvents studied. In CH(3)CN, the fr...
Journal of Organometallic Chemistry, 2013
A new water soluble Re(I) complex with a zwitterionic structure, Bu 4 N[(bpy)Re(CO) 3 (dcbpy)] (w... more A new water soluble Re(I) complex with a zwitterionic structure, Bu 4 N[(bpy)Re(CO) 3 (dcbpy)] (where Bu ¼ butyl; bpy ¼ 4,4 0 -bipyridine; dcbpy ¼ 2,2 0 -bipyridine-5,5 0 -dicarboxylate), was successfully synthesized and characterized by elemental analysis, 1 H NMR, FTIR and ESI. Protonation studies in aqueous solutions of the Re(I) complex showed three acidebase equilibriums with pK a1 ¼ 5.0, pK a2 ¼ 3.0 and pK a3 ¼ 2.0. pK a1 was assigned to the protonation equilibrium at bpy while pK a2 and pK a3 could be ascribed to protonation/deprotonation of the two carboxylates groups in the dcbpy ligand. With the aid of TD-DFT calculations the nature of the electronic transitions responsible for the pH-dependent UVevis spectroscopy of the Re(I) complex was identified. At pH ¼ 7 the lower energy band of the complex has MLLCT Re(CO)3/dcbpy character while at pH < 2 it switches to MLLCT Re(CO)3/bpy . This change in the nature of the lower energy band is responsible for the overall spectral changes in the 350e500 nm range after protonation of the Re(I) complex.
Traumatic brain injury (TBI) is a major medical and socioeconomic problem, and is the leading cau... more Traumatic brain injury (TBI) is a major medical and socioeconomic problem, and is the leading cause of death in children and young adults. The critical care management of severe TBI is largely derived from the " Guidelines for the Management of Severe Traumatic Brain Injury " that have been published by the Brain Trauma Foundation. The main objectives are prevention and treatment of intracranial hypertension and secondary brain insults, preservation of cerebral perfusion pressure (CPP), and optimization of cerebral oxygenation. In this review, the critical care management of severe TBI will be discussed with focus on monitoring, avoidance and minimization of secondary brain insults, and optimization of cerebral oxygenation and CPP.
The journal of physical chemistry. A, Jan 16, 2014
Steady state and time-resolved luminescence experiments and calorimetric studies, as well as time... more Steady state and time-resolved luminescence experiments and calorimetric studies, as well as time-dependent density functional theory calculations performed on [ClRe(CO)(3)(Bathocuproinedisulfonate)](2-), show that the photophysical properties of the Re(I) anionic complex are determined by the balance between intraligand ((1)IL) and metal-ligand-to-ligand charge transfer ((3)MLLCT) excited states. In organic solvents, (3)MLLCT states prevail and the usual expected behavior is observed: bathochromic shift of the emission maximum, a reduced luminescence quantum yield and the shortening of the excited-state lifetime upon increasing the polarity of the solvent. In addition, singlet oxygen ((1)O2) is generated with high quantum yields (Φ(Δ) ≈ 0.5 in CH(3)CN) due to the quenching of the (3)MLLCT luminescence by (3)O2. The total quenching rate constant of triplet state by oxygen, k(q), reach values between 2.2 and 2.4 × 10(9) M(-1) s(-1) for the organic solvents studied. In CH(3)CN, the fr...
Journal of Organometallic Chemistry, 2013
A new water soluble Re(I) complex with a zwitterionic structure, Bu 4 N[(bpy)Re(CO) 3 (dcbpy)] (w... more A new water soluble Re(I) complex with a zwitterionic structure, Bu 4 N[(bpy)Re(CO) 3 (dcbpy)] (where Bu ¼ butyl; bpy ¼ 4,4 0 -bipyridine; dcbpy ¼ 2,2 0 -bipyridine-5,5 0 -dicarboxylate), was successfully synthesized and characterized by elemental analysis, 1 H NMR, FTIR and ESI. Protonation studies in aqueous solutions of the Re(I) complex showed three acidebase equilibriums with pK a1 ¼ 5.0, pK a2 ¼ 3.0 and pK a3 ¼ 2.0. pK a1 was assigned to the protonation equilibrium at bpy while pK a2 and pK a3 could be ascribed to protonation/deprotonation of the two carboxylates groups in the dcbpy ligand. With the aid of TD-DFT calculations the nature of the electronic transitions responsible for the pH-dependent UVevis spectroscopy of the Re(I) complex was identified. At pH ¼ 7 the lower energy band of the complex has MLLCT Re(CO)3/dcbpy character while at pH < 2 it switches to MLLCT Re(CO)3/bpy . This change in the nature of the lower energy band is responsible for the overall spectral changes in the 350e500 nm range after protonation of the Re(I) complex.
Traumatic brain injury (TBI) is a major medical and socioeconomic problem, and is the leading cau... more Traumatic brain injury (TBI) is a major medical and socioeconomic problem, and is the leading cause of death in children and young adults. The critical care management of severe TBI is largely derived from the " Guidelines for the Management of Severe Traumatic Brain Injury " that have been published by the Brain Trauma Foundation. The main objectives are prevention and treatment of intracranial hypertension and secondary brain insults, preservation of cerebral perfusion pressure (CPP), and optimization of cerebral oxygenation. In this review, the critical care management of severe TBI will be discussed with focus on monitoring, avoidance and minimization of secondary brain insults, and optimization of cerebral oxygenation and CPP.