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K.
Travis Holman
Associate
Professor
Department of Chemistry
Georgetown
University
37th
and O Streets NW
Washington,
DC 20057-1227
Office: Basic Science 111
Phone: 202-687-4027
Fax: 202-687-6209 E-mail:
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Lab
web site |
http://www.holmanchemistry.net/ |
Education /
Background |
B.S. 1994 Saint
Mary's University
Ph.D.
1998 University
of Missouri-Columbia
NSERC
of Canada Postdoctoral
Fellow,
Dept. of Chemical Engineering and Materials
Science,
1999-2001, University of Minnesota
NSF CAREER Award (2004) |
Teaching |
Organic
Chemistry; Organic Chemistry Laboratory I; Advanced
General Chemistry; Intro to Research Experimentation,
X-Ray Crystallography, Special
Topics in Organic Chemistry
|
Research Interests |
Supramolecular
and
molecular
recognition
chemistry,
encapsulation
chemistry,
anion
binding,
organocatalysis,
solid-state
organic
chemistry,
crystal
engineering,
metal-organic
materials,
crystallography,
polymorphism,
metal-arene
chemistry
Research in the Holman lab generally lies at the
intersection of organic, organometallic, and solid-state
chemistry. Broadly, we are interested in molecular
recognition and supramolecular chemistry ― the
organization of molecules into multi-component entities
through non-covalent forces. With respect to solution
phase chemistry, our interests lead us to the design
of molecules capable of selectively binding and/or
sensing appropriate substrates, those capable of
spontaneously organizing into interesting and complex
structures, or those that might influence the organization
of other molecules, perhaps for purposes of reaction
(e.g.,
supramolecular organocatalysis). Applied to the solid-state,
we use supramolecular principals to attempt to empirically
design crystalline structure (e.g., crystal
engineering), thereby being able to impart selected
properties to materials. Research projects are inherently
multidisciplinary, allowing students to develop expertise
in synthetic organic and/or organometallic chemistry,
physical organic chemistry, solid-state organic chemistry,
powder and single crystal X-ray diffraction, various
spectroscopic techniques (NMR, neutron scattering),
thermal analysis, etc. Current projects involve:
1. Molecular
Encapsulation A principal area of research in our group involves
the synthesis and study of so-called container molecules.
As the name suggests, container molecules possess the
unique and remarkable ability to completely encapsulate
smaller, molecule-sized substrates. This feature provides
several attractive avenues for chemistry. To name but
a few, container molecules have been used for (enantio)selective
recognition and sensing, for stabilizing and characterizing
highly reactive chemical species, as micro-reaction
chambers, and to demonstrate new forms of stereo- and “social” isomerism.
Our work in this area falls into a few categories:
- Supramolecular Organocatalysis – We
are pursuing the chemical functionalization of the
cavity interiors so as to use molecular containers
as catalysts in which to perform chemical reactions.
The cavities ought to be selective with respect to
the size, shape, and chemical nature of potential reagents
which might react within their interiors. Moreover,
chiral molecular containers may function as effective
asymmetric catalysts via their ability to organize
the spatial arrangements of reactants.
- Storage Materials – The
closed-surface nature of
certain molecular containers
provides large steric barriers
to the ingress and egress
of guests. The resulting
complexes experience a corresponding
enhancement in their kinetic
stabilities. This feature
augurs well for gas separation
or storage applications
. We have initiated a program
aimed at tuning the kinetic
stabilities of materials
generally derived from container
molecules, one future goal
of which is the synthesis
of microporous materials
with novel gas storage or
separation capabilities.
Relative to traditional
clathrates and solid-state
inclusion compounds, we
have shown that materials
constructed from container-like
molecules exhibit appreciable
stability with respect to
the thermal loss of encapsulated
guests.
- Anion Binding – Modification
of the cavity exteriors with transition metal moieties
converts ostensibly electron rich, cation-binding molecular
containers, into ones which are pi-acidic and capable
of selectively binding anions. These molecules are
among the first that are specifically designed to exploit
the anion-pi interaction as a motif for selective anion
recognition.
2. Metal-Organic and Metal-Organometallic Materials
The past fifteen years have witnessed the burgeoning
of a powerful new approach in synthetic solid-state
chemistry based upon the premise that simple organic
ligands can be judiciously combined with simple transition
metal ions to give new and important materials with
controllable architectures and useful properties (e.g.,
porosity, low density, high surface area). Our own
work in the field involves the exploratory synthesis
of new metal-organic framework (MOF) materials derived
from designer-ligands which are expected to impart
unique properties. These ligands might be:
- container molecules, providing molecular recognition
and storage features
- homochiral, yielding homochiral, porous MOFs
- organometallic compounds, providing metal-derivatized
frameworks with varied properties, or
- known organocatalysts, providing opportunities
for heterogenous catalysis
3. Metal-Arene Chemistry
Appendage
of electron withdrawing transition metal moieties to
arenes dramatically affects their reactivity and supramolecular
chemistry. With respect to chemical reactivity, we are
further exploring the well-known ability of transition
metals to activate arenes toward nucleophilic attack.
For instance, we have achieved, for the first time, the
regiospecific syntheses of various arylsulfonates by
sulfodehalogenation of a series of metal-activated aryl
chlorides. We are also exploring the anion-pi interactions
of pi-acidic, metalated arenes. |
Representative
Publications |
Ugono,
O.; Holman, K. T. "An achiral form of the hexameric
resorcin[4]arene capsule sustained by hydrogen bonding
with alcohols," Chem. Commun. 2006,
2144-2146.
Fairchild, R. M.; Holman, K. T. “Selective
anion encapsulation by a metalated cryptophane with a pi-acidic
interior,” J. Am. Chem. Soc. 2005, 127,16364-16365.
Mough, S. T.; Goeltz, J. C.; Holman, K. T. “Isolation and Structure
of an ‘Imploded’ Cryptophane” Angew. Chem. Int. Ed. 2004, 43,
5631-5635.
Holman, K. T. “Cryptophanes: Molecular Containers” In Encyclopedia
of Supramolecular Chemistry; J. A. Atwood, J. W. Steed, Eds., Marcel Dekker:
New York, NY 2004; pp. 340-348.
Holman, K. T.; Hammud, H. H.; Isber S.; Tabbal, M. “One-dimensional
coordination polymer [Co(H2O)4(pyz)](NO3)2·2H2O (pyz
= pyrazine) with intra- and inter-chain H-bonds: structure, electronic spectral
studies and magnetic properties” Polyhedron, 2005, 221-228. |
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page last updated:
October 24, 2011 |