HWK Nature, 329, 529 (1987)

Polaroid image of the first molecular model of C28

C28

Mass Spectrum of Carbon Clusters

Heath, Liu, O’Brien, Curl, Kroto and Smalley unpublished data

C28

Prediction C28 tetravalent and should be stabilised by addition of four H atoms

HK Nature 1987

Prediction: because strain released and four C6 aromatic rings remain

HK Nature 1987

C28 should be a giant tetravalent “Superatom”

H W K Nature, 329, 529 (1987)

Ti

Properties of C28 in detail starting with Ti@C28

with Paul Dunk and Alan Marshall

U@C28 1993

U

800750700650600550500450400350300250

800750700650600550500450400350300250

m/z800750700650600550500450400350300250

U@C44

U@C36

800750700650600550500450400350300250

U@C36

800750700650600550500450400350300250

UO2

U@C28

C27

A

B

C

D

E

NHMFL FSU

Laser vaporization of a UO2-graphite target

laser fired at different points in time along the pulse pressure profile

U@C28 is clearly seen to form before larger U@Cn

species

U@C28

Exxon Data

Cox et al

JACS 110

1588 (1988)

C32

Endohedral Fullerene Comparison Spectra

Delft Buckyball Wkshp Dynamic Z

WOW

Moment

Nori Shinohara - Nagoya

Alan Marshall Dr. FT-ICR-MS

Chris Hendrickson

Nathan Kaiser

Paul Dunk

Rice Group showed that under intense laser irradiation C60 lost C2 fragments sequentially and at C32 blew up completely into small carbon species and atoms

C60 → C58 → C56 → → → → C32 → C2 C2 C2 Cn

(n small)

C28 should be special - a tetravalent “Superatom” atom

H W Kroto, Nature, 329, 529 (1987)

Polaroid image of the first molecular model of C28

Mass spectrum of laser vapourised graphite (Rice 1985)

C28

Sussex NNC

Sussex NNC

~sp3

Four Benzenoid aromatic rings remain

Exxon Data

Cox et al

JACS 110

1588 (1988)

NB

No C22 possible!

http://www.orchidpalms.com/polyhedra/acrohedra/nearmiss/jsmn.htm

Sussex NNC

 The structure proposed for C28 contains four triple fused pentagons units arranged in tetrahedral symmetry.

Predicted stable and semi-stable Fullerenes

image at: www.answers.com/topic/fullerene

C28 C32 C50 C60 C70

Predicted stable and semi-stable Fullerenes

image at: www.answers.com/topic/fullerene

C28 C32 C50 C60 C70

C28 should be tetravalent

C28 should be tetravalent

U@C28

U

Ti@C28

Ti

Ti@Cn distribution (RED) vs. empty cage distribution (BLUE) for FIG (2). Clearly shows titanium has stabilized C28, and other small fullerenes.

C28 Sussex NNC

C28 ”superatom” analogue of sp3 carbon atom Suggests Td C28H4 Nature 329 529 (1987)

C28H4

at: commons.wikimedia.org/wiki/File:Endohedral_fu...

Endohedral Fullerenes can satisfy “valencies” internally

m/z388387386385384383382

387386385384383382381

100

90

80

70

60

50

40

30

20

10

0

Titanium Rod – Positive ions

M(C28) + M(Ti) = 336 + 48

= 384

C28TiPredicted

m/z388387386385384383382

387386385384383382381

100

90

80

70

60

50

40

30

20

10

0

C28TiPredicted

C32

C32C32 C32

ca 50 milliDaltons separation

Titanium Rod – Positive ions

M(C28) + M(Ti) = 336 + 48

= 384

M(C32) = 384

m/z388387386385384383382

387386385384383382381

100

90

80

70

60

50

40

30

20

10

0

Titanium Rod – Positive ions C28TiPredicted

Minus C32 mass peaks

FT-ICR-MS relative intensities of Ti@Cn vs n

24 28 32 36 40 44 48 n

100

80

60

40

20

0

Abundance rel units

Ti@C28 Ti@C38

Paul Dunk with Harry Kroto and Alan Marshall

Ti@Cn vs n

(Td) C28 more stable by 717 kJmol-1 than D2

(Td) Ti@C28 more stable by 270 kJmol-1 than D2

David E. Bean, Patrick W. Fowler, University of Sheffield

C28 (D2) C28 (Td)

image at: www.answers.com/topic/fullerene

C28 ”superatom” analogue of sp3 carbon atom Suggests Td C28H4 Nature 329 529 (1987)

C28H4

at: commons.wikimedia.org/wiki/File:Endohedral_fu...

Endohedral Fullerenes can satisfy “valencies” internally

FT-ICR-MS relative intensities of Ti@Cn vs n

24 28 32 36 40 44 48 n

100

80

60

40

20

0

Abundance rel units

Ti@C28 Ti@C38

Paul Dunk with Harry Kroto and Alan Marshall

Ti@Cn vs n

(Td) C28 more stable by 717 kJmol-1 than D2

(Td) Ti@C28 more stable by 270 kJmol-1 than D2

David E. Bean, Patrick W. Fowler, University of Sheffield

C28 (D2) C28 (Td)

For the bare cages, the tetrahedral isomer is more stable by 0.273 a.u. (717 kJmol-1). When a titanium atom is encapsulated, this gap decreases to 0.103 a.u. (270 kJmol-1), but the tetrahedral isomer remains the more stable.

David E. Bean, Patrick W. Fowler, University of Sheffield

C28 (D2) C28 (Td)

at: commons.wikimedia.org/wiki/File:Endohedral_fu...

image at: people.whitman.edu/~hoffman/

Abundance of Endohedral Fullerenes Ti@Cn vs n

24 28 32 36 40 44 48 n

100

80

60

40

20

0

Abundance rel units

Ti@C28 Ti@C38

Some of the more stable members of the fullerene family. (a) C28. (b) C32. (c) C50. (d) C60. (e) C70.

image at: www.answers.com/topic/fullerene

Abundance of Endohedral Fullerenes Ti@Cn vs n

24 28 32 36 40 44 48 n

100

80

60

40

20

0

Abundance rel units

Ti@C28 Ti@C38

For the bare cages, the tetrahedral isomer is more stable by 0.273 a.u. (717 kJmol-1). When a titanium atom is encapsulated, this gap decreases to 0.103 a.u. (270 kJmol-1), but the tetrahedral isomer remains the more stable.

David E. Bean, Patrick W. Fowler, University of Sheffield

C28 (D2) C28 (Td)