Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 22
Filtrar
1.
Spec Care Dentist ; 43(2): 152-162, 2023 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-35879828

RESUMO

AIMS: EEC is a rare syndrome characterized by the triad of ectrodactyly, ectodermal dysplasia, and orofacial clefting, along with other clinical manifestations mainly in hair, skin, and teeth. The present paper aimed to perform a scoping review to collect the most relevant studies and focused on the diagnosis and oral management of EEC syndrome in the pediatric dental setting. This review also pretended to make recommendations and map the gaps in this clinical topic. METHODS: An exhaustive electronic and manual search was conducted in four databases (PubMed, EMBASE, Google Scholar, and Dentistry & Oral Sciences Source/EBSCO) according to previously established eligibility criteria, using different combinations of keywords, MeSH terms, and Boolean operators. Titles, abstracts, and full-text articles were screened and selected by precalibrated reviewers. A data charting was also accomplished for summarizing the overview of the evidence. RESULTS: A total of 37 references were identified, and 32 titles remained after removing duplicates; then, 25 potential full-text articles were carefully reviewed. Finally, 15 relevant and most informative studies were included. Most studies were single clinical case reports. Only one descriptive retrospective study was detected. None randomized clinical trials or comparative observational studies were found. A medical/dental multidisciplinary approach is needed for the management of EEC syndrome. CONCLUSIONS: Diverse dental specialists must be involved. Pediatric dentists must play a principal role in the prevention and treatment of oral diseases; particularly the preservation of the primary and mixed dentitions, trying to achieve normal orofacial growth.


Assuntos
Fenda Labial , Fissura Palatina , Displasia Ectodérmica , Humanos , Criança , Adolescente , Estudos Retrospectivos , Displasia Ectodérmica/diagnóstico , Displasia Ectodérmica/terapia
2.
Front Med (Lausanne) ; 9: 931867, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-36117970

RESUMO

Objectives: To determine the accuracy of nodal staging in patients with prostate cancer (PCa) when 99 m Tc-nanocolloid radiotracer is injected into an index lesion (IL). Methods: This prospective study was conducted at our institution between June 2016 and October 2020. It included 64 patients with localized PCa with at least a 5% possibility for lymph node involvement in the Memorial Sloan Kettering Cancer Center nomogram, suitable for surgical treatment. All patients underwent magnetic resonance imaging (MRI) with IL and were pathologically confirmed. The day before surgery, transrectal ultrasound-guided injection (TRUS) of 99 m Tc-nanocolloid into the IL was performed. Surgical procedures included radical prostatectomy (RP), sentinel lymph node biopsy (SLNB), and extended pelvic lymphadenectomy (ePLND). Analysis was performed, including histopathological findings of RP, ePLND, and SLNB. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), false negative (FN), false positive (FP), diagnostic yield, and non-diagnostic rate were calculated. Results: A total of 1,316 lymph nodes were excised, including 1,102 from the ePLND (83.7%) and 214 (16.3%) sentinel lymph nodes (SLN). 26 SLN were dissected outside the ePLND template. The final pathology demonstrated 46 (3.5%) lymph node metastasis, 31 (67.4%) in the SLNB and 15 (32.6%) in the non-SLN ePLND. At the patient level, 18 (28.1%) patients had pN1. With a mean follow-up of 33.1 months, 4/19 (21.1%) pN1 patients had undetectable PSA, and 3/19 (15.8%) had a PSA < 0.1 ng/mL. Lymph node dissection included 20.6 lymph nodes per patient (IQR 15-24.2), with 3.3 SLNB nodes per patient (IQR 2-4.2). PPV and NPV were 100 and 97.8%, respectively. Sensitivity and specificity were 94.4 and 100%, respectively. FN was 5.5% and FP was 4.3%. Diagnostic yields were 95.3% and the non-diagnostic rate was 4.7%. Conclusion: Radiotracer injection into the prostate IL offers promising results for staging purposes in cases in which ePLND is considered. Negative SLNB is a predictor of negative ePLND. Patients with a limited burden of nodal metastasis have a significant chance of remaining free of biochemical recurrence at mid-term follow-up.

3.
Sci Rep ; 12(1): 316, 2022 01 10.
Artigo em Inglês | MEDLINE | ID: mdl-35013377

RESUMO

Microwave (MWA) and radiofrequency ablation (RFA) are main ablative techniques for hepatocellular carcinoma (HCC) and colorectal liver metastasis (MT). This randomized phase 2 clinical trial compares the effectiveness of MWA and RFA as well as morphology of corresponding ablation zones. HCC and MT patients with 1.5-4 cm tumors, suitable for ablation, were randomized into MWA or RFA Groups. The primary endpoint was short-to-long diameter ratio of ablation zone (SLR). Primary technical success (TS) and a cumulative local tumor progression (LTP) after a median 2-year follow-up were compared. Between June 2015 and April 2020, 82 patients were randomly assigned (41 patients per group). For the per-protocol analysis, five patients were excluded. MWA created larger ablation zones than RFA (p = 0.036) although without differences in SLR (0.5 for both groups, p = 0.229). The TS was achieved in 98% (46/47) and 90% (45/50) (p = 0.108), and LTP was observed in 21% (10/47) vs. 12% (6/50) (OR 1.9 [95% CI 0.66-5.3], p = 0.238) of tumors in MWA vs. RFA Group, respectively. Major complications were found in 5 cases (11%) vs. 2 cases (4%), without statistical significance. MWA and RFA show similar SLR, effectiveness and safety in liver tumors between 1.5 and 4 cm.


Assuntos
Carcinoma Hepatocelular/cirurgia , Neoplasias Colorretais/patologia , Neoplasias Hepáticas/cirurgia , Micro-Ondas/uso terapêutico , Ablação por Radiofrequência , Idoso , Idoso de 80 Anos ou mais , Carcinoma Hepatocelular/diagnóstico por imagem , Carcinoma Hepatocelular/patologia , Feminino , Humanos , Neoplasias Hepáticas/diagnóstico por imagem , Neoplasias Hepáticas/secundário , Masculino , Micro-Ondas/efeitos adversos , Pessoa de Meia-Idade , Estudos Prospectivos , Ablação por Radiofrequência/efeitos adversos , Método Simples-Cego , Espanha , Fatores de Tempo , Resultado do Tratamento , Carga Tumoral
4.
J Forensic Sci ; 66(3): 1085-1093, 2021 May.
Artigo em Inglês | MEDLINE | ID: mdl-33547641

RESUMO

Development of latent prints employing cyanoacrylate ester (CA) can be a multistep process including CA fuming and subsequent fluorescent staining to produce fingerprints of sufficient contrast for comparison work. To enable a single-step CA fuming-staining process, a selection of fluorophores have been developed as sublimation dyes in CA fuming. A greater array of such luminescent sublimation dyes would allow users greater flexibility in selecting a particular dye-CA combination to best suit their processing needs. Toward this end, six benzoic acid derivatives were evaluated for use as luminescent sublimation dyes under elementary CA fuming conditions using a single non-porous surface type and an inexpensive handheld UV lamp for excitation. Two benzoic acid derivatives, 2-hydroxybenzoic acid (salicylic acid) and 2-aminobenzoic acid (anthranilic acid), were identified as new potential luminescent sublimation dyes with stained fingerprints excited at 254 nm. The fluorescence intensity and stability of prints produced via the sublimation of CA with 2-hydroxybenzoic acid and 2-aminobenzoic acid were evaluated over approximately six weeks using image and statistical analysis.

5.
BJR Case Rep ; 5(2): 20170024, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-31501692

RESUMO

Endometriosis of the appendix is a very rare entity and commonly affects females in childbearing age. Clinical presentation might be confusing varying from asymptomatic to acute abdominal pain and often mimicks acute appendicitis or chronic pelvic pain. Diagnosis is generally made after pathological examination as operative findings are usually non-specific. This condition poses a diagnostic challenge to radiologists and surgeons altogether and we therefore report a case of a middle aged female who presented with both right lower quadrant and right lower back pain. Recent literature is reviewed and radiological findings discussed.

6.
Pancreatology ; 16(5): 791-7, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-27592205

RESUMO

BACKGROUND: For consistent reporting and better comparison of data in research the revised Atlanta classification (RAC) proposes new computed tomography (CT) criteria to describe the morphology of acute pancreatitis (AP). The aim of this study was to analyse the interobserver agreement among radiologists in evaluating CT morphology by using the new RAC criteria in patients with AP. METHODS: Patients with a first episode of AP who obtained a CT were identified and consecutively enrolled at six European centres backwards from January 2013 to January 2012. A local radiologist at each center and a central expert radiologist scored the CTs separately using the RAC criteria. Center dependent and independent interobserver agreement was determined using Kappa statistics. RESULTS: In total, 285 patients with 388 CTs were included. For most CT criteria, interobserver agreement was moderate to substantial. In four categories, the center independent kappa values were fair: extrapancreatic necrosis (EXPN) (0.326), type of pancreatitis (0.370), characteristics of collections (0.408), and appropriate term of collections (0.356). The fair kappa values relate to discrepancies in the identification of extrapancreatic necrotic material. The local radiologists diagnosed EXPN (33% versus 59%, P < 0.0001) and non-homogeneous collections (35% versus 66%, P < 0.0001) significantly less frequent than the central expert. Cases read by the central expert showed superior correlation with clinical outcome. CONCLUSION: Diagnosis of EXPN and recognition of non-homogeneous collections show only fair agreement potentially resulting in inconsistent reporting of morphologic findings.


Assuntos
Variações Dependentes do Observador , Pancreatite Necrosante Aguda/classificação , Pancreatite Necrosante Aguda/diagnóstico , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Proteína C-Reativa/análise , Interpretação Estatística de Dados , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Insuficiência de Múltiplos Órgãos/etiologia , Insuficiência de Múltiplos Órgãos/mortalidade , Necrose , Pancreatite Necrosante Aguda/diagnóstico por imagem , Síndrome de Resposta Inflamatória Sistêmica/etiologia , Síndrome de Resposta Inflamatória Sistêmica/mortalidade , Tomografia Computadorizada por Raios X , Adulto Jovem
7.
J Nanosci Nanotechnol ; 15(9): 7272-4, 2015 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-26716322

RESUMO

Cobalt modified TiO2 and cobalt-cerium modified TiO2 were synthesized by sol gel technique using two different routes. In the first case the material was prepared by adding directly the precursor of metal (Co) during the sol-gel synthesis (In situ). The second one consisted in the impregnation of the supports of TiO2 and Ce-TiO2 prepared by sol-gel with a cobalt solution (Impregnated). The materials obtained were characterized by XRD and their textural properties were determined. The effect of the technique of synthesis as well as the presence of cerium in the photocatalytic properties of the material was evaluated in the photodegradation of phenol in aqueous phase. According to the results obtained in this study, it can be concluded that both, the integration of the metals during the sol-gel synthesis and the presence of cerium significantly improves the photocatalytic activity of TiO2.

8.
10.
Gac Med Mex ; 149(6): 673-9, 2013.
Artigo em Espanhol | MEDLINE | ID: mdl-24276191

RESUMO

Human papillomavirus (HPV)-associated oropharyngeal squamous cell carcinoma has been identified as a distinct entity within squamous cell carcinoma of the head and neck. In contrast to carcinomas associated with alcohol and/or tobacco, this subtype occurs at younger age, with frequent absence of classic risk factors, correlation with oral sexual habits, strong predilection for the palatial tonsils and the base of the tongue (lingual tonsils), basaloid or lymphoepithelial differentiation, higher degree of radiosensitivity, and overall better survival. We report two cases of lymph node, metastatic, poorly differentiated squamous cell carcinoma that were positive by immunohistochemistry for p16 with detection of HPV-16 and HPV-45 by PCR.


Assuntos
Carcinoma de Células Escamosas/complicações , Carcinoma de Células Escamosas/secundário , Neoplasias de Cabeça e Pescoço/complicações , Papillomavirus Humano 16 , Neoplasias Orofaríngeas/complicações , Neoplasias Orofaríngeas/patologia , Infecções por Papillomavirus/complicações , Idoso , Carcinoma de Células Escamosas/diagnóstico , Feminino , Neoplasias de Cabeça e Pescoço/diagnóstico , Humanos , Metástase Linfática , Masculino , Pessoa de Meia-Idade , Técnicas de Diagnóstico Molecular , Pescoço , Neoplasias Orofaríngeas/diagnóstico , Infecções por Papillomavirus/diagnóstico
11.
J Med Case Rep ; 5: 458, 2011 Sep 14.
Artigo em Inglês | MEDLINE | ID: mdl-21917161

RESUMO

INTRODUCTION: Signet-ring cell carcinoma is a rare and aggressive variant of mucinous adenocarcinoma. Only a few cases of gallbladder adenocarcinoma with signet-ring cells have been reported and because of this there is a lack of knowledge about the behavior and biology of this pathology. CASE PRESENTATION: We present the case of a 63-year-old Arab man with gallbladder signet-ring cell adenocarcinoma. He had an elective cholecystectomy and refused chemotherapy. Two months later, a small hepatic metastatic nodule was found, and nine months later he presented with multiple metastases in the liver, lymphatic nodes, both pleuras, peritoneum and subcutaneous tissue. CONCLUSION: The proliferation of signet-ring cells in a gallbladder adenocarcinoma worsens the prognosis of an already adverse neoplasm. New lines of treatment in chemotherapy, such as cisplatin, or new biological therapy, such as monoclonal antibody c-myc oncogene, should be encouraged to improve the survival and life quality of these oncologic patients.

12.
Proc West Pharmacol Soc ; 54: 15-20, 2011.
Artigo em Inglês | MEDLINE | ID: mdl-22423573

RESUMO

Parkinson's disease (PD) is characterized by malfunction of dopaminergic systems, and the current symptomatic treatment is to replace lost dopamine. For investigating mechanisms of pathogenesis and alternative treatments to compensate lack of dopamine (DA) activity in PD, the 6-hydroxydopamine (6-OHDA)-lesioned rat model of PD has been useful, these animals display apomorphine-induced contralateral rotational behavior, when they are examined after lesion. The purpose of this study was to assess Titania-dopamine (TiO2-DA) complexes implanted on the caudate nucleus for diminishing motor behavior alterations of the 6-OHDA rat model. Rats with 6-OHDA unilateral lesions received TiO2 alone or TiO2-DA implants, and were tested for open field (OF) gross motor crossing and rearing behaviors, and apomorphine-induced rotation (G) behavior. TiO2 complex have no effects on rearing OF and G behaviors, and a significant reducing effect on crossing motor behavior of normal rats compared to control non-treated rats throughout 56 days of observation. Interestingly, TiO2-DA treatment significant recovered motor crossing and rearing behaviors in 6-OHDA-lesioned rats, and diminished the G behaviors during 56 days of examination. Additionally, in the 6-OHDA-lesioned rats TiO2 treatment had a moderate recovering effect only on crossing behavior compared to lesioned non treated rats. Our results suggest that continuous release of dopamine in the caudate nucleus from TiO2-DA complex is capable of reversing gross motor deficits observed in the 6-OHDA-lesioned rat model of PD. Thistype of delivery system of DA represents a promising therapy for PD in humans.


Assuntos
Núcleo Caudado/fisiologia , Dopamina/administração & dosagem , Atividade Motora , Transtornos Parkinsonianos/terapia , Titânio/administração & dosagem , Animais , Apomorfina/farmacologia , Masculino , Transtornos Parkinsonianos/fisiopatologia , Ratos , Ratos Wistar , Rotação
13.
Endocrine ; 37(1): 1-5, 2010 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-19859842

RESUMO

A 30-year-old man was hospitalized with edema, polyuria, and abnormalities in taste. ACTH and cortisol levels at admission were markedly elevated, even after attempted suppression with 8 mg dexamethasone. A thoracic-abdominal CT revealed an anterior mediastinal lesion and hyperplasia of both adrenal glands. After excision of the mediastinal mass, which confirmed the presence of a carcinoid thymic tumor, the patient became totally asymptomatic, with normal ACTH and cortisol levels. A carcinoid thymic tumor has a poor prognosis, especially when it is associated with Cushing's syndrome. Most patients will present recidivism or metastasis within 5 years after surgery. However, the low number of cases available for analysis makes it difficult to establish optimum therapeutic approaches.


Assuntos
Tumor Carcinoide/complicações , Síndrome de Cushing/complicações , Disgeusia/complicações , Neoplasias do Timo/complicações , Adulto , Tumor Carcinoide/patologia , Tumor Carcinoide/cirurgia , Humanos , Masculino , Neoplasias do Timo/patologia , Neoplasias do Timo/cirurgia , Resultado do Tratamento
14.
World J Gastroenterol ; 15(34): 4334-8, 2009 Sep 14.
Artigo em Inglês | MEDLINE | ID: mdl-19750580

RESUMO

A 33-year-old woman who presented with epigastric discomfort and diarrhea underwent an abdominal ultrasound (US). This investigation and subsequent contrast-enhanced computed tomography, magnetic resonance imaging and endoscopic US with fine needle aspiration (FNA) revealed a 40 mm well-circumscribed mass in the uncinate process of the pancreas. Findings were suggestive of a mucinous or solid-cystic pseudopapillary tumor of the pancreas, although other lesions such as a non-functioning neuroendocrine tumor could not be ruled out. FNA samples were negative for malignant cells, but of limited value due to poor cellularity. It was decided to surgically remove the tumor because malignancy could not be discounted. Multiple intraoperative biopsies were suggestive of mesenchymal tumor and consequently a conservative resection (uncinatectomy) was performed. The postoperative course was uneventful. The definitive diagnosis was ganglioneuroma. Immunocytochemistry showed positive staining with vimentin, S-100 protein, neurofilament and neuron-specific enolase. Ganglioneuroma is a rare benign tumor that can also present as a pancreatic tumor. Uncinatectomy is feasible, safe and a good surgical technique for the treatment of non-malignant tumors located in the uncinate process of the pancreas.


Assuntos
Ganglioneuroma/diagnóstico , Ganglioneuroma/cirurgia , Pâncreas/cirurgia , Neoplasias Pancreáticas/diagnóstico , Neoplasias Pancreáticas/cirurgia , Adulto , Biópsia por Agulha Fina , Feminino , Ganglioneuroma/diagnóstico por imagem , Humanos , Imageamento por Ressonância Magnética , Pâncreas/diagnóstico por imagem , Neoplasias Pancreáticas/diagnóstico por imagem , Tomografia Computadorizada por Raios X
15.
J Phys Chem A ; 112(32): 7332-41, 2008 Aug 14.
Artigo em Inglês | MEDLINE | ID: mdl-18646735

RESUMO

Absorption spectra for 2,3-diaryl-2,3-diazabicyclo[2.2.2]octane radical cations (2(X)(*+)) and for their monoaryl analogues 2-tert-butyl-3-aryl-2,3-diazabicyclo[2.2.2]octane radical cations (1(X)(*+)) having para chloro, bromo, iodo, cyano, phenyl, and nitro substituents are reported and compared with those for the previously reported 1- and 2(H)(*+) and 1- and 2(OMe)(*+). The calculated geometries and optical absorption spectra for 2(Cl)(*+) demonstrate that p-C6H4Cl lies between p-C6H4OMe and C6H5 in its ability to stabilize the lowest energy optical transition of the radical cation, which involves electron donation from the aryl groups toward the pi*(NN)(+)-centered singly occupied molecular orbital of 2(X)(*+). Resonance Raman spectral determination of the reorganization energy for their lowest energy transitions (lambda(v)(sym)) increase in the same order, having values of 1420, 5300, and 6000 cm(-1) for X = H, Cl, and OMe, respectively. A neighboring orbital analysis using Koopmans-based calculations of relative orbital energies indicates that the diabatic aryl pi-centered molecular orbital that interacts with the dinitrogen pi system lies closest in energy to the bonding pi(NN)-centered orbital and has an electronic coupling with it of about 9200 +/- 600 cm(-1), which does not vary regularly with electron donating power of the X substituent.

16.
J Nanosci Nanotechnol ; 8(12): 6491-6, 2008 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-19205228

RESUMO

Sol-gel thin films containing Fe2o3 were deposited onto glass substrates by the dip-coating method at room temperature. Fe2O3 enriched with the isotope 57Fe was embedded in two kinds of matrices: zinc oxide (ZnO) and silica (SiO2). X-ray diffraction (XRD) was used for morphology and structure determination of the nanostructures and showed that the ZnO exhibit a wurtzite form when the film is annealed at 450 degrees C for 20 min. SiO2 thin films at C16H33PEO20:Fe2O3 = 1:2.7 x 10(-1) molar concentration exhibit a hexagonal nanophase produced by the diblock copolymer Brij58 (C16H33PEO20). Optical absorption and infrared spectroscopy techniques were used to evaluate the optical quality of the films. In order to determine if the Fe2O3 was incorporated into the matrices, room temperature Mössbauer spectra of both samples were obtained. In both cases the hematite spectrum was obtained, corroborating that the incorporation of the Fe2O3 to the matrices was done without chemical reaction whatsoever.

17.
J Nanosci Nanotechnol ; 8(12): 6569-75, 2008 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-19205242

RESUMO

We report on the photoconductive response of nanostructured sol-gel films in function of the silver nitrate concentration (ions and colloids). Silver colloids were obtained by spontaneous reduction process of Ag+ ions to Ag(0). 2-d hexagonal nanosructured sol-gel thin films were prepared by dip-coating method using the non-ionic diblock copolymer Brij58 to produce channels into the film, which house the silver nanoparticles. An optical absorption band located at 430 nm was detected by optical absorption; it corresponds to the surface plasmon. A fit to this band with modified Gans theory is presented. Photoconductivity studies were performed on films with silver ions and films with silver colloids to characterize their mechanisms of charge transport in the darkness and under illumination at 420 and 633 nm wavelengths. The films with silver colloids exhibit a photovoltaic effect stronger than the films with silver ions. While a photoconductive behaviour is observed in the films with silver ions.

18.
J Phys Chem A ; 111(25): 5441-7, 2007 Jun 28.
Artigo em Inglês | MEDLINE | ID: mdl-17542568

RESUMO

Resonance Raman and absorption spectra of 9,10-bis(2-tert-butyl-2,3-diazabicyclo[2.2.2]oct-3-yl)-anthracene (2) are measured and analyzed. The contribution of the individual vibrational normal modes to the reorganization energy is investigated. Excited-state mixed valence in this system is analyzed using density functional theory electronic structure calculations. The resonance Raman excitation profiles exhibit a resonance de-enhancement effect around 20 725 cm-1, but a corresponding feature is not observed in the absorption spectrum. This unusual observation is attributed to the presence of a dipole-forbidden, vibronically allowed component of the split mixed valence excited state. The de-enhancement dip is calculated quantitatively and explained in terms of the real and imaginary components of the polarizabilities of the two overlapping excited states.

19.
Peptides ; 28(1): 76-82, 2007 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-17161507

RESUMO

Alignment of nucleotides of APGWamide, RPCH and AKH genes gives region stretches (common regions) present in all family member variants. Common regions were separated by gap sections in the larger variants of family members. Consensus sequences for single polynucleotides from virtual hybrid molecules of DNA were obtained by joining the common regions of DNA and deleting the extra DNA nucleotides. Conceptual translation of these virtual hybrids resulted in polypeptides similar to APGWamide, RPCH and the AKH pre-pro-peptide. Virtual polypeptides were also similar to LWamide and RFamide along hydras to mammals. DNA loss probably explains the origin of neuropeptides.


Assuntos
Crustáceos/genética , DNA/genética , Evolução Molecular , Neuropeptídeos/genética , Sequência de Aminoácidos , Animais , Sequência de Bases , Crustáceos/classificação , Crustáceos/metabolismo , Dados de Sequência Molecular , Neuropeptídeos/química , Neuropeptídeos/metabolismo , Fases de Leitura Aberta/genética , Alinhamento de Sequência , Deleção de Sequência
20.
J Am Chem Soc ; 128(18): 6180-5, 2006 May 10.
Artigo em Inglês | MEDLINE | ID: mdl-16669688

RESUMO

Intramolecular photoinduced electron transfer from a hydrazine unit to an aromatic group is studied by resonance Raman spectroscopy and electronic absorption spectroscopy. Substituted hydrazine functional groups have played an important role in studies of electron-transfer reactions, photoinduced intramolecular electron transfer, and of mixed valence. A prototypical compound, 2-tert-butyl-3-(anthracen-9-yl)-2,3-diazabicyclo[2.2.2]octane, that has the hydrazine-to-anthracene charge-transfer band in a region of the visible spectrum suitable for detailed resonance Raman spectroscopy is studied in detail. Excitation profiles are obtained, calculated quantitatively by using time-dependent theoretical methods, and interpreted with the assistance of molecular orbital calculations. Excited-state distortions are calculated. The largest distortions occur on the hydrazine unit; the normal mode showing the largest distortion (659 cm(-1), calculated at 665 cm(-1)) involves an out-of-plane C-N-N-C bend consistent with removing an electron from the N-N pi antibonding orbital. Anthracene ring-centered C-C stretches also are enhanced, consistent with populating an antibonding pi orbital centered on the ring. Excellent fits to all of the excitation profiles and to the absorption band are obtained using one set of excited-state potential surfaces.

SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA