Crystal structure ofcis-[Ru(bpy)2(PPh3)Cl+][ClO 4 − ]·(toluene)·∼0.5(CH2Cl2), a species with two different disordered solvent molecules of crystallization

The complexcis-[Ru(bpy)₂(PPh₃)Cl⁺][ClO ₄ ^– ] (where bpy=2,2-bipyridyl) crystallizes from a solution in toluene/dichloromethane as the toluene-hemi(dichloromethane) solvate in the centrosymmetric space group witha=10.343(2)Å,b=11.823(3)Å,c=18.469(4)Å, =98.90(2)^o, =93.32(2)^o, =101.46(2)^o,V=2177.8(8)ų andZ=2. The structure was refined toR(F)=4.6% for those 4248 reflections above 6(F _o ). The octahedral Ru(II) cation is associated with the bond lengths Ru–Cl=2.424(2)Å, Ru–PPh₃=2.328(1) Å and Ru–N=2.045(5)–2.109(4)Å. Both the cation and the perchlorate anion are ordered. However, the unit cell also contains two disordered toluene molecules (centered about inversion centers at 1, 1/2, 0 and 1/2, 0, 1/2), and a disordered dichloromethane molecule of a partial occupancy (centered about 1/2, 0, 1).     

In silico prediction of annihilators for triplet–triplet annihilation upconversion via auxiliary-field quantum Monte Carlo

The energy of the lowest-lying triplet state (T1) relative to the ground and first-excited singlet states (S0, S1) plays a critical role in optical multiexcitonic processes of organic chromophores. Focusing on triplet–triplet annihilation (TTA) upconversion, the S0 to T1 energy gap, known as the triplet energy, is difficult to measure experimentally for most molecules of interest. Ab initio predictions can provide a useful alternative, however low-scaling electronic structure methods such as the Kohn–Sham and time-dependent variants of Density Functional Theory (DFT) rely heavily on the fraction of exact exchange chosen for a given functional, and tend to be unreliable when strong electronic correlation is present. Here, we use auxiliary-field quantum Monte Carlo (AFQMC), a scalable electronic structure method capable of accurately describing even strongly correlated molecules, to predict the triplet energies for a series of candidate annihilators for TTA upconversion, including 9,10 substituted anthracenes and substituted benzothiadiazole (BTD) and benzoselenodiazole (BSeD) compounds. We compare our results to predictions from a number of commonly used DFT functionals, as well as DLPNO-CCSD(T₀), a localized approximation to coupled cluster with singles, doubles, and perturbative triples. Together with S1 estimates from absorption/emission spectra, which are well-reproduced by TD-DFT calculations employing the range-corrected hybrid functional CAM-B3LYP, we provide predictions regarding the thermodynamic feasibility of upconversion by requiring (a) the measured T1 of the sensitizer exceeds that of the calculated T1 of the candidate annihilator, and (b) twice the T1 of the annihilator exceeds its S1 energetic value. We demonstrate a successful example of in silico discovery of a novel annihilator, phenyl-substituted BTD, and present experimental validation via low temperature phosphorescence and the presence of upconverted blue light emission when coupled to a platinum octaethylporphyrin (PtOEP) sensitizer. The BTD framework thus represents a new class of annihilators for TTA upconversion. Its chemical functionalization, guided by the computational tools utilized herein, provides a promising route towards high energy (violet to near-UV) emission.

Electronic structure theories such as AFQMC can accurately predict the low-lying excited state energetics of organic chromophores involved in triplet–triplet annihilation upconversion. A novel class of benzothiadiazole annihilators is discovered.     

Determination of mefloquine in blood, filter paper-absorbed blood and urine by 9-fluorenylmethyl chloroformate derivatization followed by liquid chromatography with fluorescence detection

We describe a method for determination of mefloquine (MQ) in 100-microliters samples of urine, whole blood, and capillary blood collected on filter paper; quantification is by liquid chromatography with fluorescence detection at 475 nm of the 9-fluorenylmethyleneoxycarbonyl derivative. Whole blood and urine samples were prepared by extraction of MQ and internal standard from aqueous base with methyl tert.-butyl ether (MTBE), separation and evaporation of the MTBE layer, and derivatization using a solution of 9-fluorenylmethyl chloroformate in acetonitrile. Filter paper spots were immersed for 16 h in 0.1 M hydrochloric acid, followed by extraction with MTBE from aqueous sodium carbonate. The separated and evaporated organic layer was treated with the derivatizing solution. An aliquot was injected onto a high-performance liquid chromatography system using a C18 reversed-phase column and acetonitrile-water (72:28) mobile phase for filter paper spot extracts as for whole blood and urine extracts. The method has a limit of determination in blood, blood spots, and urine of 50 ng/ml with 100 microliters sample size (coefficient of variation = 16%). Linearity and precision (within-day and between-day) for the method are good. The MQ derivative was isolated and characterized spectroscopically. Values for MQ concentrations in filter paper blood spots compared favorably with values found in corresponding whole blood samples analyzed by a published method.     

A tutorial and mini-review of the ICP-MS technique for determinations of transition metal ion and main group element concentration in the neurodegenerative and brain sciences

Abstract  

New techniques in the biosciences are always welcomed and important. Reviews help in updating and disseminating information in scientific fields, especially when there are many advances such as in the vital area in neuroscience. Herein is a recent review of inductively coupled plasma mass spectrometry (ICP-MS) in the context of trace elements, relating to neurodegenerative diseases. The accurate determination of such elemental distributions in Alzheimer’s disease, Parkinson’s disease, etc. allows for a better understanding of such diseases and relates to the sensitivity and scope of the ICP-MS technique. The elements detected are often “trace” and can be analyzed for both body tissues and fluids. We discuss the practical use of ICP-MS. This includes the explanations of the instrumental setup, elements and their detection limits, a brief comparison of ICP-MS with other inorganic analysis instruments, sample preparation, and the analysis method. Next, we discuss neurodegenerative disease and metal ion analysis with ICP-MS. This includes introductions to neurodegenerative diseases, tissue analysis, fluid analysis, and bioimaging of metals in brain tissue samples, and protein analysis application with metals and ICP-MS, broken down into the subtopics of (1) isotope dilution analysis, (2) related immunoassay techniques, and (3) hyphenated instrumental applications. This article is meant to be a primer for a synthetic chemist interested in utilizing this technique and is current through the middle of 2010.     

Osmium‐Mediated Oxidative Cyclizations: A Study into the Range of Initiators That Facilitate Cyclization

A general route to prepare substituted, saturated five‐membered heterocycles has been developed. The application of a wide range of starting materials to the osmium‐catalyzed oxidative cyclization reaction is described. Diols, hydroxy‐amides, hydroxy‐sulfonamides, and carbamates all cyclize in moderate to excellent yields to give cis‐tetrahydrofurans and pyrrolidines, depending upon the position of the heteroatoms in the starting materials. These cyclizations all proceed with near total selectivity for the cis‐heterocycles, and with stereospecific introduction of a hydroxy group adjacent to the ring. Moreover, routes to enantiopure starting materials are described, which give enantiopure products upon cyclization. Catalyst loadings of as low as one mol percent have been successfully employed for this transformation.     

Novel sulphur-rich BODIPY systems that enable stepwise fluorescent O-atom turn-on and H2O2 neuronal system probing

Bis-arylsulfide BODIPY systems were prepared and studied for multiple O-atom sensing (at 522 nm); 2- and 3-atom loading was optimal (50-fold, "turn on"). Neuronal studies showed greater H(2)O(2) sensitivity than 2',7'-dichlorofluorescein diacetate. The novel 1,3,6-trimethyl BODIPY formed as a biproduct under Lindsey conditions.