Selenosulfide
![](http://upload.wikimedia.org/wikipedia/commons/thumb/7/76/Dimethyl_thioselenide.svg/220px-Dimethyl_thioselenide.svg.png)
In chemistry, a selenosulfide refers to distinct classes of inorganic and organic compounds containing sulfur and selenium. The organic derivatives contain Se-S bonds, whereas the inorganic derivatives are more variable.
Organic selenosulfides
These species are classified as both organosulfur and organoselenium compounds. They are hybrids of organic disulfides and organic diselenides.
Preparation, structure, and reactivity
Selenosulfides have been prepared by the reaction of selenyl halides with thiols:[2]
- RSeCl + R'SH → RSeSR' + HCl
The equilibrium between diselenides and disulfides lies on the left:
- RSeSeR + R'SSR' 2 RSeSR'
Because of the facility of this equilibrium, many of the best characterized examples of selenosulfides are cyclic, whereby S-Se bonds are stabilized intramolecularly. One example is the 1,8-selenosulfide of naphthalene.[3] The selenium-sulfur bond length is about 220 picometers, the average of a typical S-S and Se-Se bond.
Occurrence
Selenosulfide groups can be found in almost all living organisms as part of various peroxidase enzymes, such as glutathione peroxidase and thioredoxin reductase. They are formed by the oxidative coupling of selenocysteine and cysteine residues.[2] This reaction is powered by the decomposition of cellular peroxides, which can be highly damaging and a source of oxidative stress. Selenocysteine has a lower reduction potential than cysteine, making it very suitable for proteins that are involved in antioxidant activity.[4]
Selenosulfides have been identified in some species of Allium[1] and in roasted coffee.[5] The mammalian version of the protein thioredoxin reductase contains a selenocysteine residue which forms a thioselenide (analogous to a disulfide) upon oxidation.[6]
Inorganic selenosulfides
Some inorganic selenide sulfide compounds are also known. Simplest is the material selenium sulfide, which has medicinal properties. It adopt the diverse structures of elemental sulfur but with some S atoms replaced by Se.
Other inorganic selenide sulfide compounds occur as minerals and as pigments. One example is antimony selenosulfide.
The pigment cadmium red consists of cadmium sulfoselenide. It is a solid solution of cadmium sulfide, which is yellow, and cadmium selenide, which is dark brown. It is used as an artist's pigment.[7] Unlike the organic selenosulfides and unlike selenide sulfide itself, no S-Se bond exists in CdS1−xSex or in Sb2S3−xSex.
References
- ^ a b Cai, Xiao-Jia; Uden, Peter C.; Block, Eric; Zhang, Xing; Quimby, Bruce D.; Sullivan, James J. (1994). "Allium chemistry: Identification of natural abundance organoselenium volatiles from garlic, elephant garlic, onion, and Chinese chive using headspace gas chromatography with atomic emission detection". Journal of Agricultural and Food Chemistry. 42 (10): 2081–2084. doi:10.1021/jf00046a002.
- ^ a b Hamsath, Akil; Xian, Ming (2020). "Chemistry and Chemical Biology of Selenenyl Sulfides and Thioseleninic Acids". Antioxidants & Redox Signaling. 33 (16): 1143–1157. doi:10.1089/ars.2020.8083. PMC 7698873. PMID 32151152.
- ^ Meinwald, Jerrold; Dauplaise, David; Clardy, Jon (1977). "Peri-Bridged Naphthalenes. 2. Unsymmetrical Diatomic Chalcogen Bridges". Journal of the American Chemical Society. 99 (23): 7743–7744. doi:10.1021/ja00465a074.
- ^ Byun BJ, Kang YK (May 2011). "Conformational preferences and pK(a) value of selenocysteine residue". Biopolymers. 95 (5): 345–53. doi:10.1002/bip.21581. PMID 21213257. S2CID 11002236.
- ^ Meija, Juris; Bryson, Joshua M.; Vonderheide, Anne P.; Montes-Bayón, Maria; Caruso, Joseph A. (2003). "Studies of Selenium-Containing Volatiles in Roasted Coffee". Journal of Agricultural and Food Chemistry. 51 (17): 5116–5122. doi:10.1021/jf034210h. PMID 12903978.
- ^ Lee, S.-R.; Bar-Noy, S.; Kwon, J.; Levine, R. L.; Stadtman, T. C.; Rhee, S. G. (2000). "Mammalian thioredoxin reductase: Oxidation of the C-terminal cysteine/Selenocysteine active site forms a thioselenide, and replacement of selenium with sulfur markedly reduces catalytic activity". Proceedings of the National Academy of Sciences. 97 (6): 2521–2526. Bibcode:2000PNAS...97.2521L. doi:10.1073/pnas.050579797. PMC 15961. PMID 10688911.
- ^ Hugo Müller, Wolfgang Müller, Manfred Wehner, Heike Liewald "Artists' Colors" in Ullmann's Encyclopedia of Industrial Chemistry 2002, Wiley-VCH, Weinheim. doi:10.1002/14356007.a03_143.pub2
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H2S | He | ||||||||||||||||||||
Li2S | BeS | B2S3 +BO3 | CS2 COS | (NH4)SH | O | F | Ne | ||||||||||||||
Na2S | MgS | Al2S3 | SiS SiS2 -Si | PxSy -P | -S2− 2 | Cl | Ar | ||||||||||||||
K2S | CaS | ScS Sc2S3 | TiS TiS2 Ti2S3 TiS3 | VS VS2 V2S3 | CrS Cr2S3 | MnS MnS2 | FeS Fe3S4 | CoxSy | NixSy | Cu2S CuS | ZnS | GaS Ga2S3 | GeS GeS2 -Ge | As2S3 As4S3 -As | SeS2 +Se | Br | Kr | ||||
Rb2S | SrS | Y2S3 | ZrS2 | NbS2 | MoS2 MoS3 | TcS2 Tc2S7 | Ru | Rh2S3 | PdS | Ag2S | CdS | In2S3 | SnS SnS2 -Sn | Sb2S3 Sb2S5 -Sb | TeS2 | I | Xe | ||||
Cs2S | BaS | * | LuS Lu2S3 | HfS2 | TaS2 | WS2 WS3 | ReS2 Re2S7 | OsS 4 | Ir2S3 IrS2 | PtS PtS2 | Au2S Au2S3 | HgS | Tl2S | PbS PbS2 | Bi2S3 | PoS | At | Rn | |||
Fr | Ra | ** | Lr | Rf | Db | Sg | Bh | Hs | Mt | Ds | Rg | Cn | Nh | Fl | Mc | Lv | Ts | Og | |||
* | LaS La2S3 | CeS Ce2S3 | PrS Pr2S3 | NdS Nd2S3 | PmS Pm2S3 | SmS Sm2S3 | EuS Eu2S3 | GdS Gd2S3 | TbS Tb2S3 | DyS Dy2S3 | HoS Ho2S3 | ErS Er2S3 | TmS Tm2S3 | YbS Yb2S3 | |||||||
** | Ac2S3 | ThS2 | Pa | US US2 | Np | Pu | Am | Cm | Bk | Cf | Es | Fm | Md | No |