Page 160 - Academic Press Encyclopedia of Physical Science and Technology 3rd InOrganic Chemistry

P1: GPA Final Pages
Encyclopedia of Physical Science and Technology EN007D-343 July 10, 2001 20:13

818 Inorganic Exotic Molecules

pair bonds only between pairs of adjacent atoms (also (i) From the Elizabethan philosopher and essayist
“standard valence-bond structure”). Francis Bacon: “There is no exquisite beauty
Matrix isolation The study of the structure, reactiv- without something unusual in its proportions.” 1
ity, and spectroscopy of otherwise unisolable atomic, (ii) From the early 20th century biophysicist J. S. B.
molecular, and ionic species under cryogenic condi- Haldane (quoted in Sacks, 1995): “The universe is
tions in extreme dilution in inert solvents. not only queerer than we might imagine, it is
Nano-sized molecule Molecule with a size between 1 queerer than we can imagine.”
3
and 100 nm . (iii) From the contemporary superconductivity sci-
Period Referring to position in the periodic table (also entist ... ... : “Things are counterintuitive only
see “row”). In the current study, the second period when you have intuition.”
elements include carbon and oxygen, and the third (iv) And poetry from one of the authors of this study:
row elements include silicon and sulfur. Note: Pe-
riod and row are not always synonymous in their Let us try to answer ‘what is exotic?’
numbering. We don’t respond that ‘it is ‘odd, ick’
Plemeioelectronic species Two species having a differ- Though it be real, somehow incomprehensible
ent number of electrons and the same connectivity of Descriptions many, none quite sensible
heavy atoms. The answer, Se˜nor Panza, is quixotic
Indeed to answer, may be quixotic
Pseudohalogen A linear or planar univalent radical that,
like the halogens, can form anions, salts, and covalent
This obviously suggests subjectivity in the choice of what
derivatives.
is “exotic.” As authors, we cannot profess unanimity in the
Row Referring to position in the periodic table (also see
species chosen, and, quite obviously, we cannot assume
“period”). In the current study, the first row elements
include carbon and oxygen, and the second row ele- complete agreement with all readers. What is “exotic”
ments include silicon and sulfur. Note: In the literature also involves the Zeitgeist: depending on what else has
these elements are often considered second and third been discovered or uncovered, a compound may be exotic
row, respectively. for one generation and prosaic for the next, or even the
Self-assembly Controlled formation of larger struc- otherwayaround.Acompoundfoundinaminimalcontext
tures by noncovalent interaction of two or more may be a source of glory and beauty in a more expansive,
molecules. complete story: a compound that participates in exotic
Squashing The conceptual, theoretical process of adding phenomena is assumed to belong in this article as well.
the proton that was part of an X H bond to the X Some of the molecules we will discuss are long known,
nucleus, thereby decreasing the hydrogen count by one seemingly well understood, and thus commonplace and
and increasing the nuclear charge of the heavy atom X not exotic to some readers. Even for these species, we ask
that the reader join us in our wandering and wondering.
by one.
Dare we agree with T. S. Eliot (1943):
Standard valence-bond structure See Lewis structure.
Transition metal complex Coordination compound con-
taining the d- and f-block elements. We shall not cease from exploration
Valence isoelectronic species Two species having the And the end of all our exploring
Will be to arrive where we started
same number of valence electrons and the same number
And know the place for the first time.
and connectivity of heavy atoms.
VSEPR The valence shell electron pair repulsion model,
It is now incumbent on us to try to define the term
originally introduced by Nyholm and Gillespie (with
“inorganic compound.” As with most contemporary stud-
antecedents from Sidgwick and Powell), which as-
ies, we do not take this to mean the absence of carbon,
sumes that molecular geometry associated with a cen-
as opposed to where carbon is not the dominant fea-
tral atom is determined by the number of groups (single
ture. To leave out species with carbon would force us
bonds, double bonds, triple bonds, or lone pairs) sur-
to omit endohedral metallofullerenes, organometallics,
rounding that atom.
and metal carbonyls. We also do not want to leave
out simple species such as the binary carbon oxides
CO and CO 2 as well as the hydrides C 2 H 4 and C 2 H 6 ,
WE BEGIN by acknowledging the difficulty of defining
the word “exotic.” The words “beautiful,”“weird,” and 1
From the essay “On Beauty,” quoted in Edgar Allan Poe’s “Ligea”
“counterintuitive” come to mind, for which three apho- and inscribed over the Poe Gate at the U.S. Military Academy, West
risms and a hitherto unpublished poem may help. Point, NY.