IONS IN SPACE

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IONS IN SPACE Ions are jolly little buggars,
you can almost see them Ernest
Rutherford Simon Petriea Diethard K.
Böhmeb aChemistry Department Australian National
University, Canberra ACT0200, Australia bDepartme
nt of Chemistry Centre for Research in Mass
Spectrometry Centre for Research in Earth Space
Science York University, Toronto, Canada GRC,
Ventura February 27, 2007
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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?
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• MOLECULAR IONS DETECTED SO FAR
• CH (vis), CF, CO, NO, SO
• H3 (IR), HCO, COH, HCS, N2H
• H3O, HOCO, HCNH,
• H2COH
• HC3NH
• C6H-
• NB (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),

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HISTORY OF DISCOVERY Ion Year discovered
Detection environments
-------------------------------------------------
--------------------------------------------------
--------------------------------------------------
--------------------------------------------------
--------------------------------------------------
----------------------- CH 1941
many sources HCO 1970 TMC-1,Orion KL,Sgr
B2 many sources N2H 1974
TMC-1,Orion KL,Sgr B2 many sources HCS
1981 TMC-1,Orion KL,Sgr B2 HOCO
1981 Sgr B2 HOC 1983 Sgr B2, Orion Bar
photodissociation region HCNH
1986 TMC-1, Sgr B2 H3O 1986 Orion KL,
Sgr B2 SO 1992 IC 443G shocked
molecular clump Orion Bar photodissociatio
n region CO 1993 NGC7027 planetary
nebula Orion Bar photodissociation
region HC3NH 1994
TMC-1 H3 1996 GL2136, W33A young
stellar objects
Cyg OB2 diffuse interstellar medium W33A den
se molecular cloud H2COH 1996 Orion
KL,Sgr B2,W51 giant molecular cloud CF
2006 Orion Bar C6H- 2006 TMC-1, IRC
10216 ___________________________________________
__________________________________________________
_____________________________
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Many more ions exist in the imagination
of astrochemists Negative ions. PAH anions
and cations. Organometallic cations Singly and
Multiply charged PAHs, fullerenes..
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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).
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Abundances of detected molecular ions within the
cold dense cloud TMC-1 (number densities
relative to that of predominant H2).
Fionization S fionization Ffree
electrons S fionization
(1.3x10-8)
HC3NH
Problematic if ion census is incomplete or if
electrons are attached! NB C6H-
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2. INFORMATION CONTENT OF IONS
(contd)   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 invisible connection
N2H N2 proton transfer HOCO CO2
proton transfer NH3 NH4 proton transfer
c-C3H2 c-C3H3 proton transfer
H2, H3 CH4,
CH5 CH C
caution, sources
other than PT to C
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3. Ions in Molecular Synthesis Small molecule
synthesis is well understood, e.g. H2O H
O ? O H O H2 ? OH H OH H2 ? H2O
H H2O H2 ? H3O H H3O e ? H2O H
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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
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The Special Case of C6H-
C6H e ? C6H- h?
EA(C6H) 3.8 eV
7 atoms
PAH e ? PAH- h? high
EA,
many atoms PAH- C6H ?
PAH C6H- C6H- H ? C6H2 e NB
C4H- would be very interesting because C4H is
massively abundant in IRC10216.  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 CnH
radicals.
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• But poorly understood is the ion synthesis of
• 3a. Organometallics.
• 3b. Benzene, PAHs and related molecules.
• 3c. Amino acids and larger biological molecules.

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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.
476191-194, 1997).
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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
C6H6 C4H2 ? C10H8 h? C10H8 M
? C10H8 M
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Mg(HC3N)n-1? HC3N ? Mg(HC3N)n? h?, n
? 0 Mg(HC3N)n? e ? (HC3N)n Mg
Tetracyanocyclooctatetraene (Tetracyanosemibullva
lene)
Circumstellar Envelopes Titans atmosphere
mCID
Milburn et al., J. Am. Chem. Soc. 127
(2005)13070.
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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.
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Unsuccessful attempts CH3NH2 HCOOH
CH3NH2 CO2 CH3NH2 CO H2O NH3
CH3COOH CH3COOH NH3 N-O bond
formation is preferred over C-C and N-C bond
formation. NH2OH2 CH3COOH OHO bonding
allows N-C bond formation
(Blagojevic et al., Mon. Not. R.
Astron. Soc. 339 (2003) L7-L11.)
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CO NH2OH ? NH2OH CO CH5 NH2OH ?
(NH2OH)H CH4 NH2,3OH CH3COOH CO Gly
/ CH5 Gly Gly ? CH2NH (CO
H2O) GlyH ? CH2NH2 (CO H2O)
mCID with Ar (0.14 Torr)
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-
1
-
1
?
H
kcal
mol
?
H
kcal
mol
Relative enthalpies at 0K, ?H0, for the
formation of two isomers of protonated
hydroxylamine from CH5 and NH2OH
. B3LYP/6-311G(df,pd)
0,
0,

Å
Å
0.0
0.0
Å

Å
TS
62.6
50.4
50.4
Å
Å
24.3
24.3
CH
Å
CH
4
Å
4
(Galina Orlova)
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Potential energy landscape for the reaction
between protonated hydroxyl amine and acetic acid
to produce GlyH B3LYP/6-311G(df,pd)
(Galina Orlova)
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mCID with Ar (0.14 Torr)
Top NH2OH CH3CH2COOH Middle CO ?-Ala?
?-Ala CO ?-Ala ? NH2CH2CHCO
H2O Bottom CO ?-Ala? ?-Ala
CO ?-Ala ? CH3CNH2 (COH2O)
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Potential energy landscape for the reaction
between protonated hydroxyl amine and propanoic
acid to produce ß-AlaH (solid line) and a-AlaH
(dotted line) (chondrite meteorites, aggregates
of interstellar dust, 40ß) B3LYP/6-311(df,pd)
(Galina Orlova)
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M and A represent any neutral atom / molecule
with a suitable IE. RH represents a proton
carrier with PA(R) lt PA(NH2OH). (Blagojevic
et al., Mon. Not. R. Astron. Soc. 339 (2003)
L7-L11.)
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Limits to growth?
Peptides/Proteins (CI conditions glutamic acid
/ methionine) (NH2CHRCOOH)H NH2CHRCOOH ?

(NH2CHRCONHCHRCOOH)H H2O Wincel, Fokkens,
Nibbering, Rapid Comm MS 14 (2000) 135.
(NH2CH2COOH)H CH3COOH?(CH3CONHCH2COOH)HH2O

protonated N-acetyl-glycine (CH3CONHCH2COOH)H
NH2OH ? no (clusters)
(NH2CH2CONHCH2COOH)H
H2O FeCH3CONHCH2COOH NH2OH ? ? (too
complicated) FeNH2CH2CONHCH2COOH
H2O diglycine, a dipeptide M(Gly)n
CH3COOH NH2OH ? M(Gly)n1 H2O (M assembles
the protein) larger and larger
peptides Voislav Blagojevic Ions, Biomolecules
and Catalysis SIFTing for the Origins of Life,
York U, 2005
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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 ? FeC6H6 h? FeC6H6
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
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Catalytic oxidation of benzene
M C6H6 ? MC6H6 MC6H6 O2 ? M (C6H6O2)
----------------------------------------- C6H6
O2 ? (C6H6O2) (M Fe, Cr,
Co)
Caraiman Bohme J. Phys. Chem. A 2002,
106, 9705-17.
catechol
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C602 H ? C60H2 h? -67 kcal
mol-1 C60H2 H ? C602 H2 -33 kcal
mol-1 ____________________________________________
________________________ H H ? H2 Petrie
et al, Astron. Astrophys. 271 (1991) 662. M
CH3CONHCH2COOH ? MCH3CONHCH2COOH h?
N-acetyl-glycine MCH3CONHCH2COOH NH2OH
? M NH2CH2CONHCH2COOH
H2O ______________________________________________
__________________________________________________
__________________________________________________
__________ CH3CONHCH2COOH NH2OH ?
NH2CH2CONHCH2COOH
H2O N-acetyl-glycine
diglycine, a dipeptide V. Blagojevic, Ph.D.
Dissertation, York U., 2005
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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 ? FeCmHn h? FeCmHn e ? Fe
CmHn __________________________________________
____________________________ Fe e ? Fe
h? M grain ? M(grain) h? (?) M(grain)
e ? M grain ______________________________
_____________________________________________ M
e ? M
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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
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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) lt IE(H). 2. Electron Transfer/ Electron
Detachment He X ? X2 He e - Need IE(X)
IE(X) lt 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).
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• 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,
d, into translational excitation of XH and
statistical partitioning of excess energy, -(?H
d) ET (XH) (2 d ?H) x (mC60Hn/(mC60HnmXH
)/3
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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 C6H2 e ? C6H
e ? C6H-
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Molecular Docks
Milburn et al, JPC A 103 (1999) 7528.
C602 2 HC3N ? C60 c-(HC3N)2

• Desirable Attributes
•   
• Provide atomic site (e.g. C)
• 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 the?substituent
• and so provides a new atomic
• site for further reaction, with
• ultimate charge separation. 

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Isomers of (HC3N)2
At B3LYP/6-31G(d) (top numbers) and
B3LYP/6-311G-(2df,p) (bottom numbers)
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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
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• 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

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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
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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.