Laser photodissociation caused C60 to lose C2 fragments sequentially down to C32 at which time point C32 exploded into atoms and small non-fullerene Cn species Rice Group

Instead of C32

Polaroid image of the first molecular model of C28 HWK Nature, 329, 529 (1987)

MS (Rice/Sussex unpublished result 1985)

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

Giant tetravalent “Superatom” H W Kroto, Nature, 329, 529 (1987)

FT-ICR-MS of Titanium Carbon Clusters Firing the laser at lower He pressure but still condtions to see fullerenes and rings…good conditions to investigate the rings to fullerene crossover region (C22-C30 or so). Approximate 50 mDa mass difference between Ti@C28 and empty cage C32. All spectra show POSITIVE IONS. FT-ICR-MS of Titanium Carbon Clusters 9

Ti with Paul Dunk and Alan Marshall At FSU we decided to investigate the creation and properties of C28 in detail starting with Ti@C28 Ti with Paul Dunk and Alan Marshall

U U@C28

Laser vaporization of a UO2-graphite target U@C28 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

C28 U@C28 U@C36

C28 C32 C50 C60 C70 Predicted stable and semi-stable Fullerenes image at: www.answers.com/topic/fullerene

Exxon Data Cox et al JACS 110 1588 (1988) NB No C22 possible!

FT-ICR-MS Titanium Carbon Clusters Only Cn n even clusters Ti mass 48 = 4x12 Ti@C28 Ti@C30 C27 C28 C23 C26 C31 C24 C25 C30 C29 C22 Firing the laser at lower He pressure but still condtions to see fullerenes and rings…good conditions to investigate the rings to fullerene crossover region (C22-C30 or so). Approximate 50 mDa mass difference between Ti@C28 and empty cage C32. All spectra show POSITIVE IONS. FT-ICR-MS Titanium Carbon Clusters

The detection of U@C28 confirmed that C28 is tetravalent and stabilised endohedrally Rice group 1993

Ti@C28 observed when the pure C28 is not detected Cn Ti@C28 Ti@Cn Intensities for high pressure conditions, again only even clusters(fullerenes). Ti@Cn beginning at Ti@C26 with a special abundance for Ti@C28. Clearly shows the stabilizing effect of the endohedral titanium atom…C26, C28, C30 do not form as the bare cages.

Molecular and Schlegel representations of Ti@Td-C28 Molecular and Schlegel representations of Ti@Td-C28. The internally located Ti atom is located off center, yielding additional stabilization.

Zr Zr@C28

Laser vaporization of a rod UO2 (0.8 atom %) graphite enriched with 13C amorphous carbon 10 atom % U@C28 incorporates all enriched 13C

The main isotope of Ti has mass 48 amu …so mass C32 ~ Ti@C28

Cn Ti@C28 Ti@Cn Intensities for high pressure conditions, again only even clusters(fullerenes). Ti@Cn beginning at Ti@C26 with a special abundance for Ti@C28. Clearly shows the stabilizing effect of the endohedral titanium atom…C26, C28, C30 do not form as the bare cages. no C28 25

Cn Ti@C28 Ti@Cn Intensities for high pressure conditions, again only even clusters(fullerenes). Ti@Cn beginning at Ti@C26 with a special abundance for Ti@C28. Clearly shows the stabilizing effect of the endohedral titanium atom…C26, C28, C30 do not form as the bare cages. 26

FT-ICR-MS of Titanium Carbon Clusters Firing the laser at lower He pressure but still condtions to see fullerenes and rings…good conditions to investigate the rings to fullerene crossover region (C22-C30 or so). Approximate 50 mDa mass difference between Ti@C28 and empty cage C32. All spectra show POSITIVE IONS. FT-ICR-MS of Titanium Carbon Clusters 27

FT-ICR-MS of Titanium Carbon Clusters Endohedral fullerenes even only Ti@Cn n = 32 34 36 38 Firing the laser at lower He pressure but still condtions to see fullerenes and rings…good conditions to investigate the rings to fullerene crossover region (C22-C30 or so). Approximate 50 mDa mass difference between Ti@C28 and empty cage C32. All spectra show POSITIVE IONS. FT-ICR-MS of Titanium Carbon Clusters

Electrostatic potentials neutral C28 C284- Ti@C28 Electrostatic potentials Charge is transferred from Ti and localized at the four pyramidalised carbon atoms (with Poblet)

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)

I decided to play with a molecular model kit to see what the C32 structure might be – just like a kid again

I decided to play with molecular model kit to see what C32 structure might be

Endohedral Fullerenes can satisfy “valencies” internally at: commons.wikimedia.org/wiki/File:Endohedral_fu...

U@C28 is also a highly favored species.

Electrostatic potentials neutral C28 Ti4+@C284- Electrostatic potentials Negative charge is transferred from Ti and localized at the four pyramidalised carbon atoms

FT-ICR-MS of Titanium Carbon Clusters Firing the laser at lower He pressure but still condtions to see fullerenes and rings…good conditions to investigate the rings to fullerene crossover region (C22-C30 or so). Approximate 50 mDa mass difference between Ti@C28 and empty cage C32. All spectra show POSITIVE IONS. FT-ICR-MS of Titanium Carbon Clusters 37

Zr@C28 is not as favored as Ti@C28. Zr@C28 is the smallest endohedral fullerene formed C32 is the smallest empty cage. Zr@C28 is not as favored as Ti@C28.

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

Sussex NNC

Sussex NNC

~sp3 Sussex NNC

Four Benzenoid aromatic rings remain

C44 C28 Cn Ti@C28 Ti@C44 Intensities for high pressure conditions, again only even clusters(fullerenes). Ti@Cn beginning at Ti@C26 with a special abundance for Ti@C28. Clearly shows the stabilizing effect of the endohedral titanium atom…C26, C28, C30 do not form as the bare cages. 44

Cn Ti@Cn 26 28 30 32 34 36 38 40 42 44 46 48 50 Ti@Cn distribution (Red) vs. empty cage distribution (Blue) Clearly shows titanium stabilizes C28 and other small fullerenes.