Reaction between the cationic iridacyclopentadiene complex [Ir(C4H4)(NCMe)(CO)(PPh3)2][CF3SO3] (1) and methylpropiolate produces the cationic iridabenzofuran [Ir(C7H5O{OMe-7})(CO)(PPh3)2][CF3SO3] (2) in high yield. On treatment of 2 with chloride, the carbonyl ligand is displaced and the corresponding neutral iridabenzofuran Ir(C7H5O{OMe-7})Cl(PPh3)2 (3) is formed. The fused metallacyclic rings of the iridabenzofurans 2 and 3 bear only one substituent (OMe), and therefore these compounds are well suited for studies of electrophilic aromatic substitution reactions. Bromination of cationic 2 with pyridinium tribromide proceeds to give the monobrominated iridabenzofuran [Ir(C7H5O{OMe-7}{Br-6})(CO)(PPh3)2][CF3SO3] (4) exclusively. Bromination of neutral 3 with the same reagent gives the dibrominated iridabenzofuran Ir(C7H5O{OMe-7}{Br-6}{Br-2})Br(PPh3)2 (5) exclusively. Treatment of compound 3 with mercury(II) trifluoroacetate followed by excess bromide (to displace coordinated trifluoroacetate) produces the trimercurated iridabenzofuran Ir(C7H5O{OMe-7}{HgBr-6}{HgBr-4}{HgBr-2})Br(PPh3)2 (6). The three Hg−C bonds in 6 are readily cleaved on addition of pyridinium tribromide, and the resulting product is the tribrominated iridabenzofuran Ir(C7H5O{OMe-7}{Br-6}{Br-4}{Br-2})Br(PPh3)2 (7). These regioselective mono-, di-, and trifunctionalization reactions of iridabenzofurans have been studied by DFT calculations, and the derived condensed Fukui functions have been used to rationalize the preferred sites for electrophilic attack. The crystal structures of 2−7 have been obtained.

Reaction between the diphenylacetylene complex Os(PhCtCPh)(CS)(PPh 3 ) 2 (1) and two molecules of HCtCCO 2 Me leads to a very stable, blue, osmabicylic complex with osmium at a bridgehead position. One way to consider this complex is as a metalla-aromatic molecule, viz., the osmabenzofuran Os-[C 7 H 2 O(OMe-7)(CO 2 Me-4)(Ph-1)(Ph-2)](CS)(PPh 3 ) 2 (2). The bicyclic ring system is remarkably robust, and heating this compound in ethanol at reflux with aqueous HCl effects only a transesterification of the ester function in the six-membered ring (at the 4-position), forming Os 2) with pyridinium tribromide effects bromination in the five-membered ring of the osmabenzofuran at the 6-position to form Os[C 7 HO(OMe-7)(Br-6)(CO 2 Me-4)(Ph-1)(Ph-2)](CS)(PPh 3 ) 2 (4). Crystal structure determinations of 2, 3, and 4 confirm the osmabicyclic structure of each compound. Treatment of complex 2 with anhydrous trifluoroacetic acid results in protonation at carbon atom 6 to form the cationic, tethered osmabenzene [Os[C 5 H(CH 2 CO 2 Me-5)(CO 2 Me-4)(Ph-1)(Ph-2)](CS)(PPh 3 ) 2 ]CF 3 CO 2 (5). This osmabenzene cation has also been isolated as the tri-iodide salt [Os[C 5 H(CH 2 CO 2 Me-5)(CO 2 Me-4)(Ph-1)(Ph-2)](CS)-(PPh 3 ) 2 ]I 3 (6) and the crystal structure for this complex obtained. The spectroscopic and the structural data for 2, 3, and 4 give support for the osmabenzofuran formulation for these compounds. The spectroscopic data for 5 and 6 and the structural data for 6 support the tethered osmabenzene formulation for these two compounds.

The cationic thiocarbonyl complex [Ir(CS)(MeCN)-(PPh 3 ) 2 ][CF 3 SO 3 ] (1) reacts sequentially with ethyne and LiCl to giVe the iridacyclopentadiene Ir 2), which in turn when heated with methyl triflate followed by addition of LiCl produces the stable, purple, iridabenzene Ir[C 5 H 4 (SMe-1)]Cl 2 (PPh 3 ) 2 (3). This iridabenzene undergoes electrophilic aromatic bromination in the position para to the SMe substituent to form Ir[C 5 H 3 (SMe-1)(Br-4)]Br 2 (PPh 3 ) 2 (4).

Preventing radioactive sources from being used for harmful purposes is a global challenge. A requirement for solving the challenge is developing radiation detectors that are efficient, sensitive, and practical. Room temperature semiconductor detectors (RTSDs) are an important class of gamma-ray sensors because they can generate high-resolution gamma-ray spectra at ambient operating temperatures. A number of diverse and stringent requirements must be met for semiconducting materials to serve as sensors in RTSD spectrometers, which limits the number of candidates of interest that receive attention and undergo focused research and development efforts. Despite this, the development of new compounds for sensors in RTSDs is a thriving research field, and a number of materials with stunning potential as RTSD materials have emerged within the last decade. In this perspective, the state of the art in RTSD materials is examined, and emerging semiconducting compounds are reviewed. The highly developed CdTe, CdZnTe, HgI2, and TlBr are first discussed to highlight the potential that can emerge from RTSD compounds in advanced stages of technological development. Thereafter, emerging compounds are reviewed by class from chalcogenides, iodides and chalcohalides, and organic-inorganic hybrid compounds. This work provides both a compilation of the physical and electronic properties of the emerging RTSD candidates and a perspective on the importance of material properties for the future of compounds that can transform the field of radiation detection science.

The purple osmabenzene complex Os(C5H4{SMe-1})(CF3SO3)(CO)(PPh3)2 (1) is formed in high yield through reaction between Os(C5H4{S-1})(CO)(PPh3)2 and methyl triflate. The neutral blue osmabenzenes Os(C5H4{SMe-1})(cis-X)(CO)(PPh3)2 (X = I (2a), Cl (2b), SCN (2c), CF3CO2 (2d)) are readily obtained through treatment of 1 with the appropriate anion X−. In these complexes the geometry about osmium is approximately octahedral, with the two PPh3 ligands being mutually trans and X being cis to the SMe-substituted carbon of the metallabenzene ring. When solutions of 2a in benzene are heated under reflux, the I and CO ligands interchange positions and the brown isomeric osmabenzene Os(C5H4{SMe-1})(trans-I)(CO)(PPh3)2 (3a) is formed. However, if a solution of either 2a or 3a is heated under reflux in toluene, the metal-bound carbon atoms of the osmabenzene fragment couple and a mixture of the two cyclopentadienyl complexes [Os(η5-C5H4SMe)(CO)(PPh3)2]I (4a) and Os(η5-C5H4SMe)I(CO)(PPh3) (5a) is formed. Heating solutions of 2b−d is not a viable route to the corresponding brown isomers of these compounds, because cyclopentadienyl products are formed directly. In the case of 2b a mixture of the cyclopentadienyl complexes [Os(η5-C5H4SMe)(CO)(PPh3)2]Cl (4b) and Os(η5-C5H4SMe)Cl(CO)(PPh3) (5b) is formed, while in the case of 2c [Os(η5-C5H4SMe)(CO)(PPh3)2]SCN (4c) and Os(η5-C5H4SMe)(SCN)(CO)(PPh3) (5c) are formed. In contrast, [Os(η5-C5H4SMe)(CO)(PPh3)2](CF3CO2) (4d) is the only cyclopentadienyl complex formed on heating solutions of 2d. The brown osmabenzene isomers Os(C5H4{SMe-1})(trans-X)(CO)(PPh3)2 (X = Cl (3b), SCN (3c), CF3CO2 (3d)) are accessible through treatment of 3a with AgCF3SO3, followed by addition of the appropriate anion X−. Heating the brown isomers 3a,b under the same conditions gives the same mixture of cyclopentadienyl complexes that are formed when 2a,b, respectively, are heated. However, 3c,d are resistant to thermal rearrangement and remain unchanged when heated under reflux in toluene. The crystal structures of 2c, 3c, 4d, and 5a have been obtained.

Developments in the field of organic semiconductors have generated organic photodetectors with high quantum efficiency, wide spectral sensitivity, low power consumption, and unique form factors that are flexible and conformable to their substrate shape. In this work, organic photodetectors coupled with inorganic CsI(Tl) scintillators are used to showcase the low dose rate sensitivity that is enabled when high performance organic photodetectors and scintillator crystals are integrated. The detection capability of these organic-inorganic coupled systems to high energy radiation highlights their potential as an alternative to traditional photomultiplier tubes for nuclear spectroscopy applications. When exposed to Bremsstrahlung radiation produced from an X-ray generator, SubPc:C60, AlPcCl:C70, and P3HT:PC61BM thin film photodetectors with active layer thicknesses less than 100 nm show detection of incident radiation at low and no applied bias. Remarkably low dose rates, down to at least 0.18 μGy/s, were detectable with a characteristic linear relationship between exposure rate and photodetector current output. These devices also demonstrate sensitivities as high as 5.37 mC Gy−1 cm−2 when coupled to CsI(Tl). Additionally, as the tube voltage across the X-ray generator was varied, these organic-inorganic systems showed their ability to detect a range of continuous radiation spectra spanning several hundred keV.

Some of the more attractive semiconducting compounds for ambient temperature radiation detector applications are impacted by low charge collection efficiency due to the presence of point and volumetric defects. This has been particularly true in the case of BiI3, which features very attractive properties (density, atomic number, band gap, etc.) to serve as a gamma ray detector, but has yet to demonstrate its full potential. We show that by applying growth techniques tailored to reduce defects, the spectral performance of this promising semiconductor can be realized. Gamma ray spectra from >100 keV source emissions are now obtained from high quality Sb:BiI3 bulk crystals with limited concentrations of defects (point and extended). The spectra acquired in these high quality crystals feature photopeaks with resolution of 2.2% at 662 keV. Infrared microscopy is used to compare the local microstructure between radiation sensitive and non-responsive crystals. This work demonstrates that BiI3 can be prepared in melt-grown detector-grade samples with superior quality and can acquire the spectra from a variety of gamma ray sources.

The recently synthesized cubic pyrochlore Bi 2 Ti 2 O 7 has been shown to possess displacive disorder in both the anion and cation sublattices. Here, the nature and characteristics of the displacive disorder are further investigated via vibrational spectroscopy. The infrared reflectance was measured over 30−3300 cm −1 at temperatures between 20 and 300 K, while the Raman spectra were collected from 50 to 3500 cm −1 at room temperature. It is found that Bi 2 Ti 2 O 7 exhibits more than the six modes expected in the Raman spectrum for the ideal pyrochlore structure. In addition, infrared-active modes are also present in the Raman spectra. These two results suggest displacements in the atomic positions of bismuth and oxygen away from their higher symmetry conventional pyrochlore Wyckoff positions and are strong and surprising evidence of disorder at the titanium site. Infrared-active phonon modes have been assigned to specific bending and stretching vibrational modes. The effect of the Bi ion on the O−Bi−O and O′−Bi−O′ phonon modes is discussed.