IONS IN SPACE
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(2) SCOPE 1. Molecular Ions Detected So Far. 2. Information Content of Detected Ions. 3. Ions in Molecular Synthesis. 4. Ions as Catalysts and Victims of Catalysts. 5. A Chemical Role for Multiply-Charged Ions?.
(3) 1. MOLECULAR IONS DETECTED SO FAR CH+ (vis), CF+, CO+, NO+, SO+ H3+ (IR), HCO+, COH+, HCS+, N2H+ H3O+, HOCO+, HCNH+, H2COH+ HC3NH+ C6HNB: (15 + 1 = 16), all but one positive, 2 isomeric, none multiply charged, no organometallic ions Observational biases: - need to know what to look for (spectroscopy), - need to know where to look (location),.
(4) Ion. HISTORY OF DISCOVERY Year discovered Detection environments. --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------. CH+ HCO+ N2H+ HCS+ HOCO+ HOC+ HCNH+ H3O+ SO+. 1941 1970 1974 1981 1981 1983 1986 1986 1992. CO+. 1993. HC3NH+ H3+. 1994 1996. H2COH+ CF+ C H-. 1996 2006 2006. many sources many sources many sources. TMC-1,Orion KL,Sgr B2 TMC-1,Orion KL,Sgr B2 TMC-1,Orion KL,Sgr B2 Sgr B2 Sgr B2, Orion Bar photodissociation region TMC-1, Sgr B2 Orion KL, Sgr B2 IC 443G shocked molecular clump Orion Bar photodissociation region NGC7027 planetary nebula Orion Bar photodissociation region TMC-1 GL2136, W33A young stellar objects Cyg OB2 diffuse interstellar medium W33A dense molecular cloud Orion KL,Sgr B2,W51 giant molecular cloud Orion Bar TMC-1, IRC + 10216.
(5) Many more ions exist in the imagination of astrochemists: Negative ions. PAH anions and cations. Organometallic cations Singly and Multiply charged PAHs, fullerenes...
(6) 2. INFORMATION CONTENT OF IONS a. Ions as Measures of Electron Density Ions are susceptible to spectroscopic detection, but free electrons are not. - When approximate electro-neutrality prevails, the determination of molecular ion abundance can provide a partial picture of the free-electron abundance. - Electron density is thought to determine the rate of cloud collapse, and therefore of star formation. Molecular ion measurements can provide an assay of the degree of ionization and the electron density (and so insight into the rate of star formation)..
(7) Abundances of detected molecular ions within the cold dense cloud TMC-1 (number densities relative to that of predominant H 2). Fionization ≥ Σ fionization. +. Ffree electrons ≥ Σ fionization. -9. HCO : 8 × 10. HC3NH +. -10. N2H : 5 × 10. HCS+: 1 × 10-9 HCNH+: 3 × 10-9. HC3NH+: 1 × 10-10. (1.3x10-8) Problematic if ion census is incomplete or if electrons are attached! NB: C6H-.
(8) 2. INFORMATION CONTENT OF IONS (cont’d) b. Ions as Tracers of Atoms and Molecules The detection of an ion can provide a ‘signature’ of the parent of the ion when the parent is ‘invisible’. (invisible to radioastronomers, no dipole moment) visible N2H+. invisible N2. connection proton transfer. HOCO+. CO2. proton transfer. NH3. NH4+. proton transfer. c-C3H2. c-C3H3+. proton transfer. H2, H3+ CH+. CH4, CH5+ C caution, sources other.
(9) 3. Ions in Molecular Synthesis Small molecule synthesis is well understood, e.g. H 2O. H+ + O O+ + H2 OH+ + H2 H2O+ + H2 H3O+ + e . O+ + H OH+ + H H2O+ + H H3O+ + H H2O + H.
(10) As is the ion synthesis of other small inorganic and hydrocarbon molecules:. The Ion Chemistry of Interstellar Clouds David Smith Chem. Rev. 1992, 92, 1473-1485.
(11) The Special Case of C6HC6H + e C6H- + h. EA(C6H) = 3.8 eV 7 atoms. PAH + e PAH- + h. high EA, many atoms. PAH- + C6H PAH + C6HC6H- + H C6H2 + e. NB: C4H- would be very interesting because C4H is massively abundant in IRC+10216. The cyanopolyynyl radicals like C5N are also very promising because they have EA values of 4 eV or more, so attachment is very favourable, but these radicals aren't as abundant as.
(12) But poorly understood is the ion synthesis of:. 3a. Organometallics. 3b. Benzene, PAHs and related molecules. 3c. Amino acids and larger biological molecules..
(13) 3a. Synthesis of organometallics.. A simple network of probable or possible reaction pathways for reactions of Fe+ with hydrocarbons (principally C2H2 and C4H2) and with CO under dense interstellar cloud conditions. Speculative dissociative recombination pathways are indicated by arrows featuring dotted lines; major reaction pathways are shown by bold arrows. (Petrie et al., Astrophys. J. 476:191-194, 1997)..
(14) 3b. Synthesis of benzene, PAHs, and … C+ + C3H C4+ + H C4+ + H2 C4H2+ + H C4H2+ + H C4H3+ + h C4H3+ + C2H2 (or + C2H3) C6H5+ + h (or + H) C6H5+ + H2 C6H7+ + h C6H7+ + e C6H6 + H Fe(C2H2)2+ + C2H2 FeC6H6+ + h Fe C6H6+ + e Fe + C6H6 CH. +. + C4H C H + + h.
(15) Mg(HC3N)n-1+ + HC3N Mg(HC3N)n+ + h, n 0 Mg(HC3N)n+ + e (HC3N)n + Mg Mg+. NC NC. CN. NC +e. CN. mCID. NC. CN CN. + Mg. Tetracyanocyclooctatetraene (Tetracyanosemibullvalene). Circumstellar Envelopes Titan’s atmosphere Milburn et al., J. Am. Chem. Soc. 127 (2005)13070..
(16) 3c. Synthesis of amino acids and larger biological molecules.. INTERSTELLAR GLYCINE Y.-J. Kuan, S.B. Charnley, et al. Astrophys. J. 593: 848-867 (2003) “…27 glycine lines were detected ..in one or more sources..” A RIGOROUS ATTEMPT TO VERIFY INTERSTELLAR GLYCINE L.E. Snyder et al. Astrophys. J. 619: 914-930 (2005) “We conclude that key lines necessary for an interstellar glycine identification have not yet been found.”.
(17) Unsuccessful attempts:. O. CH3NH2+ + HCOOH CH3NH2+ + CO2 CH3NH2+ + CO + H2O NH3 + CH3COOH +. NH2 OH. CH3COOH+ + NH3 N-O bond formation is preferred over C-C and N-C bond formation. NH2OH2+ + CH3COOH OH+(Blagojevic O bonding allows N-CR.bond formation et al., Mon. Not. Astron. Soc. 339 (2003) L7-L11.).
(18) CO+ + NH2OH NH2OH+ + CO CH5+ + NH2OH (NH2OH)H+ + CH4 0.8. Gly+. 0.4. CO+ + Gly / CH5+ + Gly O. GlyH+. CH2NH+. 0.6. Relative intensity. NH2,3OH + CH3COOH +. mCID with Ar (0.14 Torr). 0.2 0. GlyH+CH3COOH. NH2CH2OH+. 0.8. Gly. +. CH2NH+. 0.6. NH2. CH2NH2+. CH2NH2+. GlyH+. 0.4. OH Gly+ CH2NH+ + (CO + H2O) GlyH+ CH2NH2+ + (CO + H2O). 0.2 0 0. NH2CH2OH+ -10. -20. -30. -40 0. -10. -20. Nose cone potential /V. -30.
(19) ΔH ΔH0,0, kcal kcal mol mol-1-1. Relative enthalpies at 0K, ΔH0, for the formation of two isomers of protonated hydroxylamine from CH5+ and NH2OH .. . 0.0 0.0. TS. 62.6. 50.4 50.4. . . . . 24.324.3. CH4 . CH4. B3LYP/6-311++G(df,pd) (Galina Orlova).
(20) ΔH0, kcal mol-1. Potential energy landscape for the reaction between protonated hydroxyl amine and acetic acid to produce GlyH+. TS2. 24.3. 23.1. 0.0 -13.7 -18.8 -27.2 TS1 -54.1. B3LYP/6-311++G(df,pd) PRC2 H2O. (Galina Orlova).
(21) mCID with Ar (0.14 Torr) Top:. NH2OH+ + CH3CH2COOH Middle:. CO+ + -Ala -Ala+ +CO O. NH2. OH. -Ala+ NH2CH2CHCO+ + H2O Bottom:. CO+ + -Ala -Ala+ + CO O. NH2 OH. -Ala+ CH3CNH2+ +(CO+H2O).
(22) ΔH0, kcal mol-1 TS2-α. TS2-β TS2-α 17.4. 24.3 TS2-β 12.4 0.0. -14.5 -27.2. -19.4. TS1 -59.5. (chondrite meteorites, aggregates of interstellar dust, 40%β). -65.3. α-AlaH+ β-AlaH+. Potential energy landscape for the reaction between protonated hydroxyl amine and propanoic acid to produce β-AlaH+ (solid line) and α-AlaH+ (dotted line). H2O. B3LYP/6-311++(df,pd). (Galina Orlova).
(23) M+. NH2CH2COOH NH2CH2CH2COOH. H. M. e-. NH2CH2COOH+ NH2CH2CH2COOH+. NH3CH2COOH+ NH3CH2CH2COOH+. CH3COOH -H2O CH3CH2COOH hv/A+. NH2OH+ Interstellar gas Interstellar ice hv NH3(s) + H2O(s). CH3COOH CH3CH2COOH -H2O RH+. NH2OH. NH2OH2+. hv, heat. NH2OH. hv. NO + 3H. M and A represent any neutral atom / molecule with a suitable IE. RH+ represents a proton carrier with PA(R) < PA(NH2OH). (Blagojevic et al., Mon. Not. R. Astron. Soc. 339 (2003) L7-L11.).
(24) Limits to growth? Peptides/Proteins: (CI conditions: glutamic acid / methionine) (NH2CHRCOOH)H+ + NH2CHRCOOH (NH2CHRCONHCHRCOOH)H+ + H2 O + Wincel, Nibbering, Rapid Comm MS 14 (2000)+135. (NH2CHFokkens, 2COOH)H +CH3COOH(CH3CONHCH2COOH)H +H2O protonated N-acetyl-glycine (CH3CONHCH2COOH)H+ + NH2OH no (clusters) (NH2CH2CONHCH2COOH)H+ + H2O Fe+CH3CONHCH2COOH + NH2OH ? (too complicated) Fe+NH2CH2CONHCH2COOH + H2O diglycine, a dipeptide M+(Gly)n + CH3COOH + NH2OH M+(Gly)n+1 + H2O (M+ assembles the protein) larger and larger peptides. Voislav Blagojevic:.
(25) 4. Ions as Catalysts. Ions as catalysts of neutral reactions Atom (Molecule) Transport M+ + XO MO+ + X MO+ + Y M+ + YO ______________________________________________________. XO + Y YO + X. Bond-Activation Catalysis Fe+ + C6H6 Fe+C6H6 + h Fe+C6H6 + O2 Fe+ + (C6H6O2) _______________________________________________________________________________________________________________________________________. C6H6 + O2 (C6H6O2) + h. (see example). Bond-Formation (Recombination) Catalysis M+(grain) + O MO+(grain) MO+(grain) + CO M+(grain) + CO2 ______________________________________________________________________________________________. O + CO CO2.
(26) 1.0 0.8. +. +. ScBz. TiBz. +. VBz. M + C6H6 MC6H6 +. +. +. +. +. +. +. 0.4 0.2. Branching Ratios and k/kc. Catalytic oxidation of benzene. +. +. CrBz MnBz FeBz CoBz NiBz CuBz ZnBz. 0.6. 0.0 1.0 0.8. +. + ZrBz NbBz+ MoBz+ TcBz. YBz+. +. + RuBz+ RhBz PdBz AgBz+ CdBz+. 0.6 0.4 0.2 0.0 1.0 0.8. NA. NR +. HfBz+ TaBz+ WBz+ ReBz+ OsBz. +. LaBz. NR. IrBz+ PtBz+ AuBz+ HgBz+. 0.6 0.4 0.2 0.0. MC6H6 + O2 M + (C6H6O2) ----------------------------------------C6H6 + O2 (C6H6O2) +. NA O2 addition. addition/dehydration. O atom transfer. +. O +O O. benzene abstraction ligand switching. acetylene elimination not available or non-reaction. H = 62.5±2.5 kcal mol-1. O. H = 29.5±0.1kcal mol-1. +O. H = 16.8±0.3 kcal mol-1. OH. O O. (M = Fe, Cr, Co) + O2. H = 14.4±0.1 kcal mol-1. O O + H2 CHO CHO. Caraiman & Bohme J. Phys. Chem. A 2002, 106, 9705-17.. metal abstraction. H = -44.8±1.1 kcal mol-1. H = -52.4±0.1 kcal mol-1. C O + H2O. H = -52.6±1.1 kcal mol-1. HO OH H = -84.8±1.1 kcal mol-1. catechol.
(27) C602+ + H C60H2+ + h C60H2+ + H C602+ + H2. -67 kcal mol-1 -33 kcal mol-1. ____________________________________________________________________. H + H. H2. Petrie et al, Astron. Astrophys. 271 (1991) 662. M+ + CH3CONHCH2COOH M+CH3CONHCH2COOH + h N-acetyl-glycine M+CH3CONHCH2COOH + NH2OH M+ + NH2CH2CONHCH2COOH + H2O ____________________________________________________________________________________________________________________________________________________________. CH3CONHCH2COOH + NH2OH NH2CH2CONHCH2COOH + H2O N-acetyl-glycine diglycine, a dipeptide V. Blagojevic, Ph.D. Dissertation, York U., 2005.
(28) 4. Ions as Victims of Catalysts. Neutrals as catalysts of ion isomerization: Proton-Transport Catalysis HOC+ + H2 H3+ + CO H3+ + CO HCO+ + H2 ________________________________________________________. HOC+ HCO+. Neutrals as catalysts of ion neutralization Fe+ + CmHn Fe+CmHn + h Fe+CmHn+ + e Fe + CmHn ______________________________________________________________________. Fe+ + e Fe + h. M+ + grain M+(grain) + h (?) M+(grain) + e M + grain ___________________________________________________________________________. M+ + e M.
(29) 5. A Unique Chemical Role for Multiply-Charged Ions? Multiply charged ions: 1. Provide excess energy for products, 2. Provide electrostatic energy for reactants.. “molecular cannons” “molecular docks”.
(30) Possible Sources of Molecular Dications 1. Sequential Photoionization X + h X+ + e X+ + h X2+ + e - More important within diffuse regions (since the penetration of UV radiation within dense clouds is poor). Need IE(X +) < IE(H).. 2. Electron Transfer/ Electron Detachment He+ + X X2+ + He + e - Need IE(X) + IE(X+) < IE(He) (24.587 eV).. - More feasible with larger molecules such as PAHs and fullerenes. - Observed with naphthalene and C60.. 3. Cosmic-ray Ionization X + c.r. X2+ + c.r.’ + 2e - Has no energy restrictions, but efficiency is not known. - Likely to be of some significance throughout dense IS clouds (since cosmic rays can penetrate deep within such clouds)..
(31) “Molecular Cannons” - Charge separation reactions of heavy multiply-charged cations with light molecules can lead to the production of internally cold, but translationally hot, ions - and so provide a driving force for the subsequent occurrence of ion/neutral reactions! Petrie S, Bohme DK MNRAS 268 (1994) 103-108.. For partitioning of all of Coulombic repulsion, δ, into translational excitation of XH+ and statistical partitioning of excess energy, -(ΔH + δ) :. ET (XH+) = (2 δ – ΔH) x (mC60Hn/(mC60Hn+mXH)/3.
(32) e.g. C602+ and C60H2+ as molecular canons: C602+ + C6H6 C60+ + C6H6+ ET = 40 kcal mol-1 C60H2+ + NH3 C60+ + NH4+. ET = 53 kcal mol-1. ET often 40 to 50 kcal mol-1 ! More favorable with heavy dications, but applicable to all molecular dications. e.g. Subsequent driven ion/molecule reactions: C60H2+ + C6 C60+ + C6H+ C6H+ + H2 C6H2+ + H +. Ea ≤ 1 kcal mol-1 -.
(33) “Molecular Docks” C60 + 2 HC3N C60 + c-(HC3N)2 2+. +•. +. +. +•. Milburn et al, JPC A 103 (1999) 7528.. Desirable Attributes:. N C C CH. Provide atomic site (e.g. C) + C C CH N. +. +. N C C CH. + N C C CH. +. +. N C C CH HC C C N N C. +. · + H. C C +• C C. H. C. N. for covalent bonding. Provide sufficient charge for electrostatic attraction to overcome rehybridization energy required for bonding. Provide the intramolecular Coulomb repulsion necessary to propagate a charge to the terminus of thesubstituent and so provides a new atomic site for further reaction, with ultimate charge separation..
(34) Isomers of (HC3N)2+•. At B3LYP/6-31+G(d) (top numbers) and B3LYP/6-311++G-(2df,p) (bottom numbers).
(35) CHEMISTRY LEFT:. C602+ + HC3N C60(HC3N)2+ C60(HC3N)2+ + HC3N C60+ + (HC3N)2+ RIGHT:. HC3N+ + HC3N (HC3N)2+ mCID LEFT:. (HC3N)2+ HC6N2+ + H H2C5N+ + CN RIGHT:. (HC3N)2+ HC3N+ + HC3N HC3N+ HC2+ + CN.
(36) Parting Messages…. -A. large number of molecular ions remain to be discovered in space (given what is known about ion chemistry).. - This includes organometallic and multiply-charged cations which can have a rich chemistry. - The. role of ion catalysis in interstellar chemistry is yet to be appreciated, should increase the importance of ions in the synthesis of molecules in space.. - Space. is an ideal medium in which molecular cannons can make a chemical difference.. - Molecular dock chemistry also is very attractive and may involve a variety of multiply-charged molecules or particles.
(37) Acknowledgments Greg Koyanagi Janna Anichina Voislav Blagojevic Michael Jarvis Andrea Dasic Tuba Gozet Svitlana Shcherbyna Zhao Xiang Ping Cheng Prof. Kee Lee Jason Xu Sam Hariri Vitali Lavrov Lise Huynh Soroush Seifi.
(38) Special thanks to Simon Petrie! “Ions in Space” S. Petrie, D.K. Bohme. Mass Spectrometry Reviews 26 (2007) 258-280. “Mass Spectrometric Approaches to Interstellar Chemistry” S. Petrie, D.K. Bohme. in “Modern Methods in Mass Spectrometry” C.A. Shalley (ed.) Springer Verlag, Berlin, 2003..
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