1. Nanoclusters of Inorganic Materials: Properties, Doping and (self)assembling.

The synthesis of nanoclusters of a large variety of inorganic materials have become routine work. Concretely, hollow spherical inorganic nanoclusters of semiconducting materials, structurally related to carbon fullerenes, have been theoretically and experimentally characterized. The hollow structure of these nanoclusters allows for the design of endohedrally doped compounds, with taylored semiconducting properties, and even more, with properties (magnetism, when doping with Transition Metals) not present in the bare nanocluster. In this research line the candidate is interested on the characterization of new hollow and endohedrally doped nanoclusters of inorganic materials, such as those of semiconducting II-VI, III-V and IV elements. The considered dopants are alkali and halogens, on one hand, and transition metals on the other. Both impart a change in the gap that alters the semiconducting properties of the nanoclusters, and, in addition, the second dopants introduce magnetic properties that did not exist in the bare nanoclusters. Furthermore, these nanoclusters may be used as building blocks to assemble larger structures, such as dimers, polymers and solids. In this structures nanocluster geometries may be slightly altered with respect to isolated nanoclusters, but keeping their own structure, resembling the case of fullerites. TM doped nanoclusters can form ferromagnetic or antiferromagnetic materials, depending on the spin coupling, with possible applications in spintronics. Alkali and halogen doped materials, on the other hand, present a gap decrease as compared to bare materials, and its ionic nature enhances the conductivity, which leads to optimization of their semiconducting properties. Standard methods of Computational Chemistry based on density functional theory are used to characterize the structures of bare, doped and assembled nanoclusters, and ab initio quantum dynamics calculations are carried out to further predict the thermal stability of characterized nanoclusters.

1.1. Recent publications on the field:

* Jimenez-Izal et. al. J. Phys. Chem. C 114, 2476 (2010)
* Matxain et. al. Chem. Eur. J. 15, 5138 (2009)
* Matxain et. al. Chem. Eur. J. 14, 8547 (2008)
* Matxain et. al. ChemPhysChem 8, 2096 (2007)
* Matxain et. al. J. Phys. Chem. C 111, 13354 (2007)
* Matxain et. al. J. Phys. Chem. C 111, 3560 (2007)

2. All-Metall Aromatic Systems

Designing new chemical compounds is one of the most ambitious goals of every chemist. Nonetheless, efforts made for the understanding of the chemistry of new chemical compounds often yield new paradigms which open unexpected research areas. All-metal aromatic molecules, recently synthesized by Li et al, constitute one such an example. Indeed, rationalizing the unexpected large resonance energy of Al42- has yield the concept of multiple-fold aromaticity, as that present in molecules that posses more than one independent delocalized bonding system, either \sigma-type or \pi-type, each of them satisfying the 4n+2 electron counting rule of aromaticity. This new concept should help understanding the “simultaneously” contributions to aromaticity within the same molecular structure, as arising from various delocalized bonding systems of the molecule and, it should be of general applicability, irrespective of whether the molecule is organic or inorganic.

The all-metal aromatic Al42- molecule, therefore, is the first of the series of recently synthesized compounds that constitute a new paradigm in chemistry. These compounds present similar properties to Al42-, namely, high magnetic shielding, large ring current, similar derived antiaromatic structures and large resonance energies.

These molecules are normally prepared as singly charged anions since double charged species are expected to be rather unstable in the gas phase due to large intramolecular Coulomb repulsion. Thus, complexation with counterions is required to produce more stable species and, also convenient for mass analysis and photodetachment experiments. However, as recently putted forward by Kuznetsov  et al. ” …the question remains if the X42- aromatic rings can be incorporated into sandwich-type complexes…”, but, as far as we know, no sandwich-type complexes of these molecules have been reported up to date.

We have focused on this idea, and have been able to calculate stable sandwich-type structures which have a similar structure as metallocenes. The Al4TiAl42- has two aromatic -2 charged squares (analogous to the cyclopentadienyls in the metallocenes) and a +2 charged titanium on the center of the system.

2.1. Recent publications on the field:

• [ISI:000266484700031] J. M. Mercero, M. Piris, J. M. Matxain, X. Lopez, and J. M. Ugalde, "Sandwich Complexes of the Metalloaromatic eta(3)-Al3R3 Ligand," JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, vol. 131, iss. 20, p. 6949, 2009.
  Show bibtex
  @ARTICLE{ISI:000266484700031,
  author = {Mercero, Jose M. and Piris, Mario and Matxain, Jon M. and Lopez, Xabier and Ugalde, Jesus M.},
  title = {{Sandwich Complexes of the Metalloaromatic eta(3)-Al3R3 Ligand}},
  journal = {{JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}},
  year = {{2009}},
  volume = {{131}},
  pages = {{6949+}},
  number = {{20}},
  month = {{MAY 27}},
  __markedentry = {[pobmelat]},
  abstract = {{Metal sandwich complexes made of metallic Al3R3 aromatic three-membered rings have been characterized, and their structural and electronic properties have been studied using density functional theory. The perfluorinated cyclotrialane ring has been identified as a very stable ligand for sandwichlike complexation, as it bears both large sigma and large pi aromaticities. We have demonstrated that the perfluorocyclotrialane ligand can sandwich metals and metal dimers while retaining its aromaticity upon complexation. Also, we have found that atomic magnetism is preserved upon complexation of magnetic transition-metal atoms. Finally, we have studied the assembly of these sandwichlike complexes into linear polymer-like structures.}},
  address = {{1155 16TH ST, NW, WASHINGTON, DC 20036 USA}},
  affiliation = {{Mercero, JM (Reprint Author), Euskal Herriko Unibertsitatea \& Donostia Int Phys, Kim Fak, PK 1072, Donostia San Sebastian 20080, Euskadi, Spain. {[}Mercero, Jose M.; Piris, Mario; Matxain, Jon M.; Lopez, Xabier; Ugalde, Jesus M.] Euskal Herriko Unibertsitatea \& Donostia Int Phys, Kim Fak, Donostia San Sebastian 20080, Euskadi, Spain.}},
  author-email = {{jm.mercero@ehu.es}},
  doc-delivery-number = {{451QM}},
  doi = {{10.1021/ja8095043}},
  issn = {{0002-7863}},
  journal-iso = {{J. Am. Chem. Soc.}},
  keywords-plus = {{MG-MG BONDS; MOLECULAR-STRUCTURE; CLUSTERS; AL; ALUMINUM; MES=2,4,6-ME(3)C(6)H(2); CHEMISTRY; ZN; GA}},
  language = {{English}},
  number-of-cited-references = {{24}},
  publisher = {{AMER CHEMICAL SOC}},
  subject-category = {{Chemistry, Multidisciplinary}},
  times-cited = {{1}},
  type = {{Article}},
  unique-id = {{ISI:000266484700031}}
}
• [ISI:000238263900002] J. Mercero, E. Formoso, J. Matxain, L. Eriksson, and J. Ugalde, "Sandwich complexes based on the “All-Metal” Al-4(2-) aromatic ring," CHEMISTRY-A EUROPEAN JOURNAL, vol. 12, iss. 17, p. 4495-4502, 2006.
  Show bibtex
  @ARTICLE{ISI:000238263900002,
  author = {Mercero, JM and Formoso, E and Matxain, JM and Eriksson, LA and Ugalde, JM},
  title = {{Sandwich complexes based on the ``All-Metal{''} Al-4(2-) aromatic ring}},
  journal = {{CHEMISTRY-A EUROPEAN JOURNAL}},
  year = {{2006}},
  volume = {{12}},
  pages = {{4495-4502}},
  number = {{17}},
  month = {{JUN 2}},
  __markedentry = {[pobmelat]},
  abstract = {{We report on novel sandwichlike structures {[}Al4MAl4](q-) (q=0-2 and M=Ti, V, Cr, Zr, Nb, Mo, Hf, Ta and W) based on the recently synthesized all-metal aromatic Al-4(2-) square ring. The sandwichlike structures have two aromatic tetraaluminum square rings which trap a transition-metal cation from either the first, second, or third row. The stability of the anionic sandwichlike complexes towards electron detachment is discussed, and addition of alkali cations is found to stabilize the 2- charged complexes, preventing spontaneous electron detachment. Once the sandwichlike complexes are formed, the Al-4(2-) square properties remain nearly unchanged; this fact strongly supports the hypothesis that in these complexes the Al-4(2-) square rings remain aromatic.}},
  address = {{PO BOX 10 11 61, D-69451 WEINHEIM, GERMANY}},
  affiliation = {{Mercero, JM (Reprint Author), Euskal Herriko Unibertsitatea, Kim Fak, PK 1072, Donostia San Sebastian 20080, Euskadi, Spain. Euskal Herriko Unibertsitatea, Kim Fak, Donostia San Sebastian 20080, Euskadi, Spain. DIPC, Donostia San Sebastian 20080, Euskadi, Spain. Univ Orebro, Dept Nat Sci, S-70182 Orebro, Sweden. Univ Orebro, Orebro Life Sci Ctr, S-70182 Orebro, Sweden.}},
  author-email = {{jm.mercero@ehu.es}},
  doc-delivery-number = {{052WF}},
  doi = {{10.1002/chem.200600106}},
  issn = {{0947-6539}},
  journal-iso = {{Chem.-Eur. J.}},
  keywords = {{aluminum; aromaticity; density functional calculations; sandwich complexes; transition metals}},
  keywords-plus = {{D-ORBITAL AROMATICITY; ANTIAROMATIC MOLECULE; CLUSTERS; ANALOGS; HYDROCARBONS; SYSTEMS; ENERGY}},
  language = {{English}},
  number-of-cited-references = {{35}},
  publisher = {{WILEY-V C H VERLAG GMBH}},
  subject-category = {{Chemistry, Multidisciplinary}},
  times-cited = {{18}},
  type = {{Article}},
  unique-id = {{ISI:000238263900002}}
}
• [ISI:000224686700011] J. Mercero, J. Matxain, and J. Ugalde, "Mono- and multidecker sandwich-like complexes of the tetraazacyclobutadiene aromatic ring," ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, vol. 43, iss. 41, p. 5485-5488, 2004.
  Show bibtex
  @ARTICLE{ISI:000224686700011,
  author = {Mercero, JM and Matxain, JM and Ugalde, JM},
  title = {{Mono- and multidecker sandwich-like complexes of the tetraazacyclobutadiene aromatic ring}},
  journal = {{ANGEWANDTE CHEMIE-INTERNATIONAL EDITION}},
  year = {{2004}},
  volume = {{43}},
  pages = {{5485-5488}},
  number = {{41}},
  __markedentry = {[pobmelat]},
  address = {{PO BOX 10 11 61, D-69451 WEINHEIM, GERMANY}},
  affiliation = {{Mercero, JM (Reprint Author), Euskal Herriko Unibertsitatea, Kimika Fak, PK 1072, Euskadi, Spain. Euskal Herriko Unibertsitatea, Kimika Fak, Euskadi, Spain.}},
  author-email = {{pobmelat@sq.ehu.es}},
  doc-delivery-number = {{865FA}},
  doi = {{10.1002/anie.200460498}},
  issn = {{1433-7851}},
  journal-iso = {{Angew. Chem.-Int. Edit.}},
  keywords = {{aromaticity; density functional calculations; sandwich complexes; transition metals}},
  keywords-plus = {{GAS-PHASE; CLUSTERS}},
  language = {{English}},
  number-of-cited-references = {{23}},
  publisher = {{WILEY-V C H VERLAG GMBH}},
  subject-category = {{Chemistry, Multidisciplinary}},
  times-cited = {{31}},
  type = {{Article}},
  unique-id = {{ISI:000224686700011}}
}
• [ISI:000220286400006] J. Mercero and J. Ugalde, "Sandwich-like complexes based on “all-metal” (Al-4(2-)) aromatic compounds," JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, vol. 126, iss. 11, p. 3380-3381, 2004.
  Show bibtex
  @ARTICLE{ISI:000220286400006,
  author = {Mercero, JM and Ugalde, JM},
  title = {{Sandwich-like complexes based on ``all-metal{''} (Al-4(2-)) aromatic compounds}},
  journal = {{JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}},
  year = {{2004}},
  volume = {{126}},
  pages = {{3380-3381}},
  number = {{11}},
  month = {{MAR 24}},
  __markedentry = {[pobmelat]},
  address = {{1155 16TH ST, NW, WASHINGTON, DC 20036 USA}},
  affiliation = {{Mercero, JM (Reprint Author), Euskal Herriko Unibertsitatea, Kim Fak, PK 1072, Donostia San Sebastian 20080, Euskadi, Spain. Euskal Herriko Unibertsitatea, Kim Fak, Donostia San Sebastian 20080, Euskadi, Spain.}},
  author-email = {{pobmelat@sq.ehu.es}},
  doc-delivery-number = {{804GE}},
  doi = {{10.1021/ja039074b}},
  issn = {{0002-7863}},
  journal-iso = {{J. Am. Chem. Soc.}},
  keywords-plus = {{MOLECULES; CLUSTERS}},
  language = {{English}},
  number-of-cited-references = {{15}},
  publisher = {{AMER CHEMICAL SOC}},
  subject-category = {{Chemistry, Multidisciplinary}},
  times-cited = {{56}},
  type = {{Article}},
  unique-id = {{ISI:000220286400006}}
}