In the beginning, like attracts like to make a dimer. Nobel Prizes are a rich source of dimers. I counted twenty-three Nobel Lectures with dimers. The wealth in dimers can compound a case not only in biochemistry but also in organic chemistry. A new certainty sparkles here with a metal form, the beryllium dimer.
Beryllium is a fascinating metal of sweetness. Would you remember Be and its compounds are too toxic for a taste? Nevertheless, early experimenters were led to lick to their demise. Moreover, breathtakingly precious emerald and aquamarine contain beryl [Be3Al2(SiO3)6], a product of star evolution and one of 30 Be mineral sources. Beryllium itself belongs to the first quarter hour of the Big Bang. Carbon formation has followed the process in stars. Only the last century, however, highlighted Be's unique properties, including a dimer possibility.
A dimer's presence, Be2, was settled in 2009 by experimental data as well as theoretical calculations. There were two teams at work on the matter, one at Emory University with Technical University Munich (Germany) and another at University of Delaware in cooperation with the Institute of Organic Chemistry and Biochemistry (Czech Republic). Jeremy Merritt's team took spectroscopic measurements of the molecule's ground electronic state with sufficient resolution to recognize 11 vibrational levels. Performed in Michael Heaven's laboratory, the experiment allowed recording and analyzing spectra that sampled all the bound vibrational levels of the beryllium dimer molecule’s electronic ground state. The second team utilized the possibility that a twelfth level existed just below the dissociation threshold remained unresolved. Konrad Patkowski and colleagues found a potential function that supports the presence of the twelfth vibrational level. This potential, once fitted to experimental data, reproduced the observed spectra to within 0.1 cm–1. There is the beryllium dimer (Be2) after all -- beyond the previous disagreements. Shown by chemists and physicists in Science, the results were repeated in Nature. The bond is quite small -- 2.45 angstroms -- in the order of hydrogen bonds.
There is glamor in dimers. The term was defined in 1926, or 67 years after "diatomic molecules." Yet I could count fewer than 23 -- only 22 -- Nobel Lectures with "diatomic" over that time. Dimers for a Nobel, anyone?
Notes and references:
1. Merritt, J., et al. (2009) Beryllium dimer - caught in the the act of bonding. Science, 324: 1548 - 1551. DOI: 10.1126/science.1174326.
2. Patkowski, K., et al. (2009) On the elusive twelfth vibrational state of beryllium dimer. Science, 326: 1382-1384. DOI: 10.1126/science.1181017.