We present the synthesis, photophysical characterization, and electrochemistry of three series of cyclometalated binuclear platinum(II) complexes, each bridged by two 3,5-disubstituted pyrazolate ...ligands (μ-R2pz). These neutral compounds have the general formula C∧NPt(μ-R2pz)2, where C∧N is a cyclometalating ligand corresponding to 2-(2′-thienyl)pyridine (thpy), 1-phenylisoquinoline (piq), or 7,8-benzoquinoline (bzq) with R = H, Me, iPr, Ph, corresponding to series I–III dimers, respectively. Systematic variation of the cyclometalating ligands in addition to the bridging pyrazolates renders colorful structures exhibiting a range of electrochemical and spectroscopic behavior with absorption and photoluminescence properties tuned over a wide portion of the visible spectrum. Steric bulk introduced into the 3,5-positions on the pz bridges readily modulates intramolecular d8–d8 metal–metal σ interactions strongly affecting the frontier orbitals’ electronic structure, manifested by changes in absorption and emission energy, excited-state lifetime, and photoluminescence quantum yield. Cyclic voltammetry revealed the presence of two very closely spaced reversible C∧N ligand-based reductions ranging between −1.97 and −2.56 V vs Fc+/Fc, and the first metal–metal-centered oxidation wave was found to be reversible in dichloromethane and irreversible in coordinating THF in most instances. All the complexes of series I displayed triplet ligand-localized excited states at all temperatures, while an increase of steric bulk in the pz bridge in the two other molecular series resulted in a variation of photophysical behavior ranging from charge transfer to ligand localized, including admixture behavior.
N,N-Di(6-phenylpyridin-2-yl)aniline (L1), N,N-di(6-(2,4-difluorophenyl)pyridin-2-yl)aniline (L2), N,N-di(3-(pyridin-2-yl)phenyl)aniline (L3), N,N-di(3-(1H-pyrazol-1-yl)phenyl)aniline (L4), ...N,N-di(3-(3-methyl-1H-pyrazol-1-yl)phenyl)aniline (L5), and N,N-di(3-(4-methyl-1H-pyrazol-1-yl)phenyl)aniline (L6) undergo cyclometalation to produce two types of tetradentate bis-cyclometalated platinum(II) complexes: C∧N*N∧C platinum complexes 1 and 2 and N∧C*C∧N platinum complexes 3−6, respectively, where an “X∧Y” (X, Y = C or N) denotes a bidentate coordination to the platinum to form a five-membered metallacycle and “X*Y” denotes a coordination to form a six-membered metallacycle. The crystal structures of 1, 3, and 5 were determined by the single-crystal X-ray diffraction analysis, showing distorted square-planar geometry, that is, two C∧N coordination moieties are twisted. Complex 5 showed much greater distortion with largest deviation of 0.193 Å from the mean NCCNPt coordination plane, which is attributed to the steric interaction between the two 3-methyl groups on the pyrazolyl rings. Density functional theory (DFT) calculations were carried out on the ground states of 1 and 3−6. The optimized geometries are consistent with the crystal structures. The highest occupied molecular orbitals (HOMOs) and lowest unoccupied molecular orbitals (LUMOs) of the molecules displayed a localized characteristic with the contribution (18−45%) of the platinum metal to the HOMOs. All complexes are emissive at ambient temperature in fluid with quantum yields of 0.14 to 0.76 in 2-methyltetrahydrofuran. The emission of the complexes covers from blue to red region with λmax ranging from 474 to 613 nm. Excimer emission was observed for 1 and 2 at high concentration of the complexes. The emission lifetime at infinite dilution for 1 and 2 was determined to be 7.8 and 11.4 μs, respectively. Concentration quenching was observed for 3 and 4, but the excimer emission was not observed. The life times for 3−6 were determined to be in the range of micro seconds, but those of 4−6 (3.4−5.7 μs) were somewhat shorter than that of 3 (7.6 μs). The highly structured emission spectra, long life times, and DFT calculations suggested that the emissive state is primarily a 3LC state with metal-to-ligand charge-transfer (MLCT) admixture. The ZFS of 23 cm−1 for the emissive triplet state was observed directly by high resolution spectroscopy for 1 in a Shpol’skii matrix, which also suggested an emission from a triplet ligand centered (3LC) state with admixture of MLCT character. Complex 1 was incorporated into an organic light-emitting diode (OLED) device as an emitter at 4 wt % in the mixed host of 4,4′,4′′-tris(N-carbazolyl)triphenylamine (TCTA) and 2,2′,2′′-(1,3,5-benzenetriyl)tris(1-phenyl-1-H-benzimidazole) (TPBI) and demonstrated excellent performance with maximum external quantum efficiency of 14.7% at the current density of 0.01 mA/cm−1.
The synthesis and photophysics of a new Re(I)-carbonyl diimine complex, Re(PNI-phen)(CO)3Cl, where the PNI-phen is N-(1,10-phenanthroline)-4-(1-piperidinyl)naphthalene-1,8-dicarboximide is reported. ...The metal-to-ligand charge transfer (MLCT) emission lifetime was increased approximately 3000-fold at room temperature with respect to that of the model complex Re(phen)(CO)3Cl as a result of thermal equilibrium between the emissive 3MLCT state and a long-lived triplet ligand-centered (3LC) state on the PNI chromophore. This represents the longest excited state lifetime (τ = 651 μs) that has ever been observed for a Re(I)-based CT photoluminescence at room temperature. The energy transfer processes and the associated rate constants leading to the establishment of the excited state equilibrium were elucidated by a powerful combination of three techniques (transient visible and infrared (IR) absorption and photoluminescence), each applied from ultrafast to the micro/milliseconds time scale. The MLCT excited state was monitored by transient IR using CO vibrations through time intervals where the corresponding signals obtained in conventional visible transient absorption were completely obscured by overlap with strong transients originating from the pendant PNI chromophore. Following initial excitation of the 1LC state on the PNI chromophore, energy is transferred to form the MLCT state with a time constant of 45 ps, a value confirmed in all three measurement domains within experimental error. Although transient spectroscopy confirms the production of the 3MLCT state on ultrafast time scales, Förster resonance energy transfer calculations using the spectral properties of the two chromophores support initial singlet transfer from 1PNI* to produce the 1MLCT state by the agreement with the experimentally observed energy transfer time constant and efficiency. Intersystem crossing from the 1MLCT to the 3MLCT excited state is believed to be extremely fast and was not resolved with the current experiments. Finally, triplet energy was transferred from the 3MLCT to the PNI-centered 3LC state in less than 15 ns, ultimately achieving equilibrium between the two excited states. Subsequent relaxation to the ground state occurred via emission resulting from thermal population of the 3MLCT state with a resultant lifetime of 651 μs. The title chromophore represents an interesting example of “ping-pong” energy transfer wherein photon excitation first migrates away from the initially prepared 1PNI* excited state and then ultimately returns to this moiety as a long-lived excited triplet which disposes of its energy by equilibrating with the photoluminescent Re(I) MLCT excited state.
Molecular organization of donor–acceptor pairs within a metal–organic framework (MOF) offers a new approach to improving energy and charge transfer at donor–acceptor interfaces. Here, the ...photo-physical effects of infiltrating MOF-177 (ZnO 4 (BTB) 2 ; BTB = 1,3,5-benzenetribenzoate) with α,ω-dihexylsexithiophene (DH6T) and 6,6-phenyl-C 61 -butyric acid methyl ester (PCBM), representing well-established polymeric and molecular materials used in organic photovoltaics, were probed using UV-visible absorption and luminescence spectroscopies combined with first-principles electronic structure calculations. The energetics of guest molecule infiltration were determined by constructing potential energy curves from self-consistent charge density-functional tight-binding (SCC-DFTB) calculations. These reveal that infiltration is energetically favored and that DH6T and PCBM are strongly bound to MOF-177 by 55 kcal mol −1 and 57 kcal mol −1 , respectively. Solution-phase infiltration with PCBM achieved a 22 wt% loading, comparable to those in bulk heterojunction solar cells, but without evidence of phase segregation. DH6T loadings were very light (maximum of ∼1 molecule per 11 unit cells), but this was sufficient to produce significant quenching of the MOF-177 photoluminescence (PL). The coincident appearance of DH6T PL demonstrates that efficient Förster resonance energy transfer (FRET) from the MOF-177 linkers to DH6T occurs. These results show that the MOF is a multifunctional host that not only confines and stabilizes guest molecules, but also plays an active role, serving as a photon antenna that harvests light not efficiently absorbed by a donor molecule (DH6T in this case) and transferring it to guest acceptor molecules. Finally, time-dependent density functional theory (TDDFT) predicts the existence of linker-to-PCBM charge transfer states, suggesting that photoconductivity might be achievable in an appropriately designed guest@MOF system.
Hematite occurs in various geologic settings including igneous, metamorphic, and sedimentary rocks as well as in soils. However, it frequently occurs at low concentrations, especially in soils, where ...it may be <1% by weight. Because hematite has the potential to be an indicator of oxidizing and climatic conditions in soils and paleosols, it is important to understand its limit of detection. In this paper we examine the limits of detection of hematite visually and with diffuse reflectance spectrophotometry (DRS) and X-ray diffraction (XRD). To accomplish this we used a sample set consisting of "knowns" or calibration samples. These known samples consisted of 15 different matrices of varying mineral composition into which hematite in 7 different concentrations ranging from 0.01 to 4% by weight were mixed. Including the 0% hematite, our calibration data set consisted of 120 samples. Visually, hematite can be detected at a concentration of 0.01% by weight in a light matrix and 0.5% in the darkest of our matrices. However, because of metamerism, visual techniques cannot specifically identify hematite. We find that for both DRS and XRD the limit of detection is also dependent on the matrix. For XRD the limit of detection for hematite in bulk samples is about 1%. For DRS the limit of detection depends on the data reduction technique used. The commonly used Kubelka-Munk remission function and its first and second derivatives can easily identify hematite at the 0.5% level. However, the first derivative of the percent reflectance curve can detect hematite at 0.01% by weight in a light matrix and 0.05% in a dark matrix. We suggest that the first derivative of DRS curves is the best currently available method for qualitatively detecting the mineral hematite at low concentrations found in soils, sediments, and rocks. Work described in this paper may be applied in several situations. Our study of visual limits of hematite detection should aid field geologists in assessing hematite content. Analysis of color wavelength bands may also have application in remote sensing by indicating which bands are most sensitive to hematite, reported to be an important constituent of the martian surface. Furthermore, this study could help clarify remotely sensed terrestrial albedo changes, especially the Sahara/Sahel transition where the sediments change from light, quartz-dominated to dark, hematite-dominated. Our study also points out that with laboratory-based spectra the first derivative of the reflectance curve is the most sensitive transform for processing spectral data for hematite, thereby allowing concentrations as low as 0.01% to be detected.
Pulmonary rehabilitation (PR) reduces the number and duration of hospital admissions and readmissions, and improves health-related quality of life in patients with COPD. Despite clinical guideline ...recommendations, under-referral and limited uptake to PR contribute to poor treatment access. We reviewed published literature on the effectiveness of interventions to improve referral to and uptake of PR in patients with COPD when compared to standard care, alternative interventions, or no intervention. The review followed recognized methods. Search terms included "pulmonary rehabilitation" AND "referral" OR "uptake" applied to MEDLINE, EMBASE, CINAHL, PsycINFO, ASSIA, BNI, Web of Science, and Cochrane Library up to January 2018. Titles, abstracts, and full papers were reviewed independently and quality appraised. The protocol was registered (PROSPERO # 2016:CRD42016043762). We screened 5,328 references. Fourteen papers met the inclusion criteria. Ten assessed referral and five assessed uptake (46,146 patients, 409 clinicians, 82 hospital departments, 122 general practices). One was a systematic review which assessed uptake. Designs, interventions, and scope of studies were diverse, often part of multifaceted evidence-based management of COPD. Examples included computer-based prompts at practice nurse review, patient information, clinician education, and financial incentives. Four studies reported statistically significant improvements in referral (range 3.5%-36%). Two studies reported statistically significant increases in uptake (range 18%-21.5%). Most studies had methodological and reporting limitations. Meta-analysis was not conducted due to heterogeneity of study designs. This review demonstrates the range of approaches aimed at increasing referral and uptake to PR but identifies limited evidence of effectiveness due to the heterogeneity and limitations of study designs. Research using robust methods with clear descriptions of intervention, setting, and target population is required to optimize access to PR across a range of settings.
Abstract
Aims
Electronic health (eHealth) sources have great potential to improve patients’ access to health information for self-management of secondary prevention after percutaneous coronary ...intervention (PCI). It remains unclear, however, whether patients are health-related digitally active and whether they have sufficient eHealth literacy. This study aimed to determine the extent to which patients after PCI are health-related digitally active at baseline, 2 and 6 months after PCI, and to determine the association between patients’ eHealth literacy and their health-related digital activity.
Methods and results
This multicentre cohort study included patients at three large referral PCI centres in Norway (n = 1970). Data were collected from medical records, national registries, and patients’ self-reports. The eHealth Literacy Scale (eHEALS) assessed patients’ eHealth literacy. At baseline, 67% had used the internet to find health information. The mean eHEALS score was 25.71 (standard deviation 6.22), illustrating a lower level of eHealth literacy. There were substantial associations between eHealth literacy and use of the internet to find health information coefficient 10.90, 95% confidence interval (CI) 8.05–14.57. At the 2-month follow-up, there were substantial associations between baseline eHealth literacy and use of the internet to find information about health, prevention, illness, or treatment odds ratio (OR) 1.19, 95% CI 1.14–1.24 and use of health applications (OR 1.15, 95% CI 1.08–1.22).
Conclusion
This study provides evidence that patients’ level of eHealth literacy after PCI is associated to how patients use, and can make use of, eHealth technology for health information.
Registration
ClinicalTrials.gov (NCT03810612).
Graphical Abstract
Graphical Abstract
Three acridinone-based molecules ADBP, ACBP, and DABP were synthesized, and their application to the OLED devices was investigated. When used as the host for either the deep blue singlet or the green ...triplet emitter in OLED devices, the bipolar molecules ADBP and ACBP demonstrated superior performance compared to either DABP or commonly used host CBP, remarkably lowering the drive voltage and improving efficiencies.
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