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PODSTAWY CHEMII
SUPRAMOLEKULARNEJ Z
ELEMENTAMI NANO –
NIEKONWENCJONALNIE
PODSTAWOWE POJĘCIA
Marek Pietraszkiewicz, Instytut Chemii Fizycznej PAN, 01-224
Warszawa, Kasprzaka 44/52, tel: 3433416
E-mail: [email protected]
DEFINICJA CHEMII SUPRAMOLEKULARNEJ
Supramolecular chemistry is a relatively new field of chemistry which focuses
quite literally on going "beyond" molecular chemistry. It can be described as the
study of systems which contain more than one molecule, and it aims to
understand the structure, function, and properties of these assemblies. Interest in
supramolecular chemistry arose when chemistry had become a relatively mature
subject and the synthesis and properties of molecular compounds had become
well understood. The domain of supramolecular chemistry came of age when
Donald J. Cram, Jean-Marie Lehn, and Charles J. Pedersen were jointly awarded
the Nobel Prize for Chemistry in 1987 in recognition of their work on "host-guest"
assemblies (in which a host molecule recognises and selectively binds a certain
guest). Other examples of supramolecular systems include biological
membranes, polynuclear metal complexes, liquid crystals, and molecule-based
crystals. Even a cell can be envisaged as a (very complex!) supramolecular
system and indeed recent research has targeted assemblies involving
biopolymers such as nucleic acids, and proteins.
DEFINICJA CHEMII SUPRAMOLEKULARNEJ
This is defined as the chemistry of molecular assemblies and of the intermolecular bond,
as "chemistry beyond the molecule", bearing on the organized entities of higher complexity
that result from the association of two or more chemical species held together by
intermolecular forces. Thus, supramolecular chemistry may be considered to represent a
generalized coordination chemistry extending beyond the coordination of transition
elements by organic and inorganic ligands to the bonding of all kinds of substrates;
cationic, anionic and neutral species of either inorganic, organic or biological nature.
Jean-Marie Lehn stated: "Supramolecular chemistry is the chemistry of the intermolecular
bond, concerning the structure and functions of the entiies fromed by the association of
two or more chemical species." from Edwin Constable, "Metallosupramolecular
Chemistry", Chemistry & Industry, 17 January, 1994
An intermolecular bond is a generic term that includes ion pairing (electrostatic),
hydrophobic and hydrophillic interactions, hydrogen-bonding, host-guest interactions, pistacking, and Van der Walls interactions. Some would also include the coordinate bond in
this list if the role of the metal is to act as an attachment template.
DEFINICJE – c.d.
Self-Assembly: The ideal supramolecular system requires only mixing of the component
compounds in order to produce the desired aggregate. The idea of spontaneous selfassembly comes into play becasue the molecular components are 'preorganized' and thus
contain information in the form of molecular recognition features that are mutally
complementary. "The architectural and functional features of organized supramolecular
structures result from the molecular information stored in the components and from the
active groups which they bear." (Lehn)
Cooperativity: Cooperativity may also be considered to be a 'molecular
amplification' device because once a process is initiated, the
subsequent steps occur more easily if the initial interaction causes a
conformation change that prepares the compound for the next
attractive recognition process. The zipping up of a DNA molecule is a
good example of a cooperative supramolecular process.
DEFINICJE – c.d.
Lattice Energy: The lattice energy, U, of an ionic solid is generally defined asthe energy
change associated with the process of going from solid to gas:
MX(s) --> M+(g) + X-(g)
The lattice energy receives contributions from electrostatic, repulsive, dispersive, and
the zero-point energy. (Seddon)
Synthon: "Supermolecular synthons are structural units within supermolecules which
can be formed and/or assembled by known or conceivable synthetic operations involving
intermolecular interactions." (Desiraju) The recognition and use of these spacial
arrangements of intermolecular interactions follows the same lines as in conventional
organic synthesis.
ELEKTROUJEMNOŚĆ
The affinity for electrons.
The atoms of the various elements differ in their affinity for electrons.
This image distorts the conventional periodic table of the elements so that the
greater the electronegativity of an atom, the higher its position in the table.
ELEKTROUJEMNOŚĆ
H
2.20
Pauling Electronegativity Scale
Li
0.98
Be
1.57
B
2.04
C
2.55
N
3.04
O
3.44
F
3.98
Na
0.93
Mg
1.31
Al
1.61
Si
1.90
P
2.19
S
2.58
Cl
3.16
K
0.82
Ca
1.00
Sc
1.36
Ti
1.54
V
1.63
Cr
1.66
Mn
1.55
Fe
1.83
Co
1.88
Ni
1.91
Cu
2.00
Zn
1.65
Ga
1.81
Ge
2.01
As
2.18
Se
2.55
Br
2.96
Rb
0.82
Sr
0.95
Y
1.22
Zr
1.33
Nb
1.60
Mo
2.16
Te
1.90
Ru
2.20
Rh
2.28
Pd
2.20
Ag
1.93
Cd
1.69
In
1.78
Sn
1.96
Sb
2.05
Te
2.10
I
2.66
Cs
0.79
Ba
0.89
La
1.10
Hf
1.30
Ta
1.50
W
2.36
Re
1.90
Os
2.20
Ir
2.20
Pt
2.28
Au
2.54
Hg
2.00
Tl
2.04
Pb
2.33
Bi
2.02
Po
2.00
At
2.20
Allred-Rochow Electronegativity Scale
H
2.20
Li
0.97
Be
1.47
B
2.01
C
2.50
N
3.07
O
3.50
F
4.10
Na
1.01
Mg
1.23
Al
1.47
Si
1.74
P
2.06
S
2.44
Cl
2.83
K
0.91
Ca
1.04
Sc
1.20
Ti
1.32
V
1.45
Cr
1.56
Mn
1.60
Fe
1.64
Co
1.70
Ni
1.75
Cu
1.75
Zn
1.66
Ga
1.82
Ge
2.02
As
2.20
Se
2.48
Br
2.74
Rb
0.89
Sr
0.99
Y
1.11
Zr
1.22
Nb
1.23
Mo
1.30
Te
1.36
Ru
1.42
Rh
1.45
Pd
1.35
Ag
1.42
Cd
1.46
In
1.49
Sn
1.72
Sb
1.82
Te
2.01
I
2.21
Cs
0.86
Ba
0.97
La
1.08
Hf
1.23
Ta
1.33
W
1.40
Re
1.46
Os
1.52
Ir
1.55
Pt
1.44
Au
1.42
Hg
1.44
Tl
1.44
Pb
1.55
Bi
1.67
Po
1.76
At
1.90
Although fluorine (F) is the most electronegative element, it
is the electronegativity of runner-up oxygen (O) that is
exploited by life.
•The relative electronegativity of two interacting atoms also
plays a major part in determining what kind of chemical bond
forms between them.
Example 1: Sodium (Na) and Chlorine (Cl) = Ionic Bond
•There is a large difference in electronegativity, so
•the chlorine atom takes an electron from the sodium atom
•converting the atoms into ions (Na+) and (Cl-).
•These are held together by their opposite electrical charge forming ionic bonds.
•Each sodium ion is held by 6 chloride ions while each chloride ion is, in turn, held by 6 sodium
ions.
Result: a crystal lattice (not molecules) of common table salt (NaCl).
Example 2: Carbon (C) and Oxygen (O) = Covalent Bond
•there is only a small difference in electronegativity, so
•the two atoms share the electrons
•Result: a covalent bond (depicted as C:H or C-H)
•atoms held together by the mutual affinity for their shared electrons
•an array of atoms held together by covalent bonds forms a true molecule.
Example 3:Hydrogen (H) and Oxygen (O) = Polar Covalent Bond
•moderate difference in electronegativity, so
•oxygen atom pulls the electron of the hydrogen atom closer to itself
•Result: a polar covalent bond
•Oxygen does this with 2 hydrogen atoms to form a molecule of water
The carbon-fluorine bond
Fluorine is much more electronegative than carbon. The actual values on
the Pauling scale are
Carbon 2.5
Fluorine 4.0
That means that fluorine attracts the bonding pair much more strongly than
carbon does. The bond - on average - will look like this:
The carbon-oxygen double bond
An orbital model of the C=O bond in methanal, HCHO, looks like this:
POLARYZOWALNOŚĆ
Ability of an ion to distort the electron cloud of another.
Large amount of polarization - electrons shared between
elements - covalent bonding.
A small positive ion favours covalency
very high charge/volume ratio
highly polarizing
attracts electron density of negative ion
e.g., LiH more nearly covalent than NaH
Example 1
Changing cation size
MCl2
6 co-ord.
radius (pm)
m.p. (°C)
Be2+
59
405
smaller, more
polarizing, more
covalent, lower m.p.
Example 2
Increasing anion size
LiX
6 co-ord. anion
radius (pm)
m.p. (°C)
LiF
119
870
LiCl
167
613
LiBr
182
547
LiI
206
446
largest anion,
most
polarizable,
most covalent
Example 3
Increasing charge of cation
MBrx
Cation
charge
m.p.
(°C)
NaBr
+1
755
MgBr2
+2
700
AlBr3
+3
97.5
lowest charge,
least polarizing,
most ionic
KONCEPCJE KWASÓW I ZASAD
Compound
Ka
pKa
ConjugateBase
Kb
pKb
HI
3 x 109
-9.5
I-
3 x 10-24
23.5
HCl
1 x 106
-6
Cl-
1 x 10-20
20
H2SO4
1 x 103
-3
HSO4-
1 x 10-17
17
H3O+
55
-1.7
H2O
1.8 x 10-16
15.7
HNO3
28
-1.4
NO3-
3.6 x 10-16
15.4
H3PO4
7.1 x 10-3
2.1
H2PO4-
1.4 x 10-12
11.9
CH3CO2H
1.8 x 10-5
4.7
CH3CO2-
5.6 x 10-10
9.3
H2S
1.0 x 10-7
7.0
HS-
1 x 10-7
7.0
H2O
1.8 x 10-16
15.7
OH-
55
-1.7
CH3OH
1 x 10-18
18
CH3O-
1 x 104
-4
HCCH
1 x 10-25
25
HCC-
1 x 1011
-11
NH3
1 x 10-33
33
NH2-
1 x 1019
-19
H2
1 x 10-35
35
H-
1 x 1021
-21
CH2=CH2
1 x 10-44
44
CH2=CH-
1 x 1030
-30
CH4
1 x 10-49
49
CH3-
1 x 1035
-35
Koncepcja Lewisa kwasów i zasad
In the Lewis theory of acid-base reactions, bases donate
pairs of electrons and acids accept pairs of electrons. A
Lewis acid is therefore any substance, such as the H+ ion,
that can accept a pair of nonbonding electrons. In other
words, a Lewis acid is an electron-pair acceptor. A Lewis
base is any substance, such as the OH- ion, that can
donate a pair of nonbonding electrons. A Lewis base is
therefore an electron-pair donor.
WIĄZANIA CHEMICZNE
Covalent Bonding
Ionic substances:
•usually brittle
•high melting point
•organized into an ordered lattice of atoms, which can be cleaved along a smooth line
the electrostatic forces organize the ions of ionic substances into a rigid,
organized three-dimensional arrangement
The vast majority of chemical substances are not ionic in nature
•gases and liquids, in addition to solids
•low melting temperatures
Bond energy is always a positive value - it takes energy to break a covalent
bond (conversely energy is released during bond formation)
Bond
(kJ/mol)
C-F
485
C-Cl
328
C-Br
276
C-I
240
C-C
348
C-N
293
C-O
358
C-F
485
C-C
348
C=C
614
C=C
839
Average bond
energies
RODZAJE ODDZIAŁYWAŃ
MIĘDZYCZĄSTECZKOWYCH
• WIĄZANIE WODOROWE
• WIĄZANIE KOORDYNACYJNE
• WIĄZANIE JONOWE
• ODDZIAŁYWANIA VAN DER WAALSA
• ODDZIAŁYWANIA PI-STAKINGOWE
• SIŁY POLIDYSPERSYJNE
RODZAJE ODDZIAŁYWAŃ
MIĘDZYCZĄSTECZKOWYCH
dipole-dipole interaction. dipole-dipole force.
Electrostatic attraction between oppositely charged poles of two or more dipoles
electric dipole moment. (µ) dipole moment.
A measure of the degree of polarity of a polar molecule*. Dipole moment is a vector with
magnitude equal to charge separation times the distance between the centers of positive
and negative charges. Chemists point the vector from the positive to the negative pole;
physicists point it the opposite way. Dipole moments are often expressed in units called
Debyes
hydrogen bond. hydrogen bonding.
An especially strong dipole-dipole* force between molecules X-H...Y, where X and Y are
small electronegative atoms (usually F, N, or O) and ... denotes the hydrogen bond.
Hydrogen bonds are responsible for the unique properties of water and they loosely pin
biological polymers like proteins and DNA into their characteristic shapes.
RODZAJE ODDZIAŁYWAŃ
MIĘDZYCZĄSTECZKOWYCH
intermolecular force.
An attraction or repulsion between molecules. Intermolecular forces are much weaker
than chemical bonds. Hydrogen bonds, dipole-dipole interactions, and London forces are
examples of intermolecular forces.
London force. dispersion force.
An intermolecular attractive force that arises from a cooperative oscillation of electron
clouds on a collection of molecules at close range.
van der Waals force.
A force acting between nonbonded atoms or molecules. Includes dipole-dipole, dipoleinduced dipole, and London forces.
MY NAME IS BOND…
HYDROGEN BOND…
WIĄZANIE WODOROWE
The evidence for hydrogen bonding
Many elements form compounds with hydrogen - referred to as "hydrides".
If you plot the boiling points of the hydrides of the Group 4 elements, you
find that the boiling points increase as you go down the group. The
increase in boiling point happens because the molecules are getting larger
with more electrons, and so van der Waals dispersion forces become
greater
WIĄZANIE WODOROWE
If you repeat this exercise with the hydrides of elements in Groups 5, 6 and
7, something odd happens. Although for the most part the trend is exactly
the same as in group 4 (for exactly the same reasons), the boiling point of
the hydride of the first element in each group is abnormally high. In the
cases of NH3, H2O and HF there must be some additional intermolecular
forces of attraction, requiring significantly more heat energy to break.
These relatively powerful intermolecular forces are described as hydrogen
bonds.
WIĄZANIE WODOROWE
GRUPY ATOMÓW ZAANGAŻOWANE W WIĄZANIA
WODOROWE:
N-H, O-H, F-H, C-H
CH-kwasy: CH3NO2, CH2(CO2Et)2
WIĄZANIE WODOROWE
The origin of hydrogen bonding
The molecules which have this extra bonding are:
WIĄZANIE HYDROFOBOWE
The Hydrophobic bond
ΔG= ΔH−TΔS
Equilibrium when ΔG = 0. G is Gibbs’free energy, the enthalpy is H = E + PV,
Tis absolute temperature and S is the entropy. The process goes
spontaneously from left to right when ΔG< 0. Find the position of
thermodynamic equilibrium for a well-known example of insolubility:
CH4 in benzene→CH4 in H2O
The experimental data show (all units in calories per mol):ΔG = ΔH −T ΔS +
2600 = −2800 −298(−18)
+2600 = −2800 + 5400
Conclusion: Insolubility of paraffin in water due to entropy loss, not to enthalpy
change!
ODDZIAŁYWANIA VAN DER WAALSA
Dipole-Dipole forces are one of van der Waals' three forces. Dipole Dipole
forces occur in polar molecules, that is, molecules that have an unequal sharing
of electrons. For example, HCl comprised of the atom Hydrogen and Chlorine is
polar. The Chlorine atom has an extra electron, which came from the hydrogen
atom. Because of this, the chlorine part of the molecule is negatively charged,
and the hydrogen side of the molecule is positively charged.
ie. H - Cl
+
-
So in a solution where there are thousands of these molecules around that are
slightly charged on each side, the molecules naturally orient themselves the
accommodate the charge. The positive part of one molecule will move until it is
next to the negative part of a neighboring molecule. These forces between
molecules tend to make them 'stick' together.
ODDZIAŁYWANIA VAN DER WAALSA
Dispersion forces are another of van der Waals' three
forces. They exist between nonpolar molecules. For
example, chlorine gas is made up of two chlorine atoms. In
this bond, the electrons are equally shared and are not
dominant on one side of the molecule as is the case in HCl.
The atom looks like this
Cl - Cl
ODDZIAŁYWANIA VAN DER WAALSA
van der Waals forces: dispersion forces
Dispersion forces (one of the two types of van der Waals force we
are dealing with on this page) are also known as "London forces"
(named after Fritz London who first suggested how they might
arise).
The origin of van der Waals dispersion forces
Temporary fluctuating dipoles
Attractions are electrical in nature. In a symmetrical molecule like
hydrogen, however, there doesn't seem to be any electrical
distortion to produce positive or negative parts. But that's only
true on average.
ODDZIAŁYWANIA VAN DER WAALSA
How temporary dipoles give rise to intermolecular attractions
Imagine a molecule which has a temporary polarity being approached by one which
happens to be entirely non-polar just at that moment. (A pretty unlikely event, but it
makes the diagrams much easier to draw! In reality, one of the molecules is likely to
have a greater polarity than the other at that time - and so will be the dominant one.)
As the right hand molecule approaches, its electrons will tend to be attracted by the
slightly positive end of the left hand one.
This sets up an induced dipole in the approaching molecule, which is orientated in
such a way that the + end of one is attracted to the - end of the other.
WIĄZANIA KOORDYNACYJNE
J.-M. LEHN
WIĄZANIA KOORDYNACYJNE
J.-M. LEHN
WIĄZANIA KOORDYNACYJNE
J.-M. LEHN
Assembly of Hydrogen Bonded Diamondoid Networks Based on Synthetic MetalOrganic Tetrahedral Nodes
Bao-Qing Ma,* Hao-Ling Sun, and Song Gao* , Inorg. Chem., 44, 837 (2005)
DONORY I AKCEPTORY ELEKTRONÓW
N
N
N
RO
OR
N
OR
S
S
S
S
M2+
O
O
M = Co, Ni, Cu
N
NC
CN
C
CN
NC
CN
N
O
O
N
R
O
Cl
Cl
Cl
Cl
O
CN
C
Cl
CN
Cl
CN
Fe
O
R
R
N
O
O
N
O
O
O
F
F
F
F
O
O
O
N
R
O
ODDZIAŁYWANIA PI-STAKINGOWE
H
C8H17
C8H17
C8H17
C8H17
N
N
N
N
N
N
N
H
O
H
H
N
O
N
O
N
H
H
N
N
C8H17
O
N
N
H
H
S
S
S
S
S
H
H
H
O
N
O
N
N
H
O
N
N
H
C8H17
H
N
N
N
N
C8H17
N
N
C8H17
N
H
N
O
N
O
O
N
O
H
H
N
N
H
N
C8H17
H
H
S
H
H
O
O
S
O
N
N
H
H
S
N
N
N
N
H
O
H
N
C8H17
O
H
N
N
N
N
C8H17
N
H
C8H17
KONCEPCJA: RECEPTOR MOLEKULARNY –
SUBSTRAT
RECEPTOR: CZĄSTECZKA ZDOLNA DO „WCHŁONIĘCIA”
MNIEJSZEJ CZĄSTECZKI DZIEKI ODDZIAŁYWANIOM
NIEKOWALENCYJNYM
Projektowanie, synteza, architektura molekularna zdolna do
wykonywania określonych wcześniej funkcji
SUBSTRAT: MAŁA CZĄSTECZKA, KOMPLEMENTARNA
ROZMIAREM Z LUKĄ RECEPTORA
Substrat: jony nieorganiczne i organiczne, cząsteczki obojętne,
kompleksy koordynacyjne, związki metaloorganiczne
KONCEPCJA: RECEPTOR MOLEKULARNY –
SUBSTRAT
GRUPY FUNKCYJNE:
ELEKTRONODONOROWE: OR, OAr, Cl, Br, J, NR, S, P
ELEKTROAKCEPTOROWE: F, NO2, CO2H, SO3H
PRZEGLĄD RECEPTORÓW MOLEKULARNYCH
• RECEPTORY ACYKLICZNE
• ETERY KORONOWE
• PODANDY
• MAKROCYKLICZNE POLIAMINY
• KRYPTANDY
• CYKLOFANY
• SFERANDY
• TORANDY
• CYKLODEKSTRYNY
•.ROTAKSANY
• KATENANDY
• WĘZŁY MOLEKULARNE
• KALIKSARENY
• HELIKATY
RECEPTORY ACYKLICZNE
MeO
MeO
MeO
H2
C
O
O
O
S
S
S
N
H
N
H
O
S
N
H
O
S
OMe
OMe
OMe
ETERY KORONOWE
O
O
O
O
O
O
O
O
O
O
12-CROWN-4
O
O
O
O
O
OC18H37
O
O
18-CROWN-6
O
H37C18O
O
O
15-CROWN-5
CH3 O
O
O
5
PODANDY
X
X
X
N
NR
R
N
N
N
NR
RN
NR
RN
RN
N
R
N
N
R = H, Me, ligating group
N
X
X
H
N
O
O
X =
O
O
X
Si ( OEt ) 3
H
N
H
N
O
Si ( OEt ) 3
MAKROCYKLICZNE POLIAMINY
N
N
H
H
NH
H
N
N
N
H
H
NH
HN
NH
HN
HN
H
N
H
N
H
N
KRYPTANDY
N
N
N
N
N
N
N
N
N
N
N
O
O
N
Eu3+
O
O
O
O
CYKLOFANY
SFERANDY
D.J. CRAM
TORANDY
N
N
N
N
N
N
CYKLODEKSTRYNY
What are cyclodextrins?
ROTAKSANY
Figure 2. Cartoon representation of a [2]rotaxane.
KATENANDY
Figure 1. Cartoon representation of a [2]catenane.
WĘZŁY MOLEKULARNE
J.-P. Sauvage
KALIKSARENY
X
HO
OH
R
R
OH
HO
X
X
OH
HO
R
R
OH
HO
X
HELIKATY
DENDRYMERY
NH2
NH2
N
N
N
H2N
H
H
N
N
H2N
N
N
O
O
N
H2N
N
O
N
N
NH2
N
N
H
N
N
O
NH2
H2N
O
O
H
N
NH2
H
H
NH2
N
N
NH2
NH2
FUNKCJE RECEPTORÓW MOLEKULARNYCH
• TRANSPORT
• KATALIZA
• ROZPOZNANIE
• STABILIZACJA RZADKICH STANÓW REDOX
• TRANSFORMACJA SUBSTRATU
• REAKCJA FOTOCHEMICZNA
• KONWERSJA ENERGII ŚWIETLNEJ
• ALLOSTERIA
INTERNETOWE PORTALE SPECJALISTYCZNE –
MOŻLIWOŚCI
http://nanotechweb.org
http://www.scirus.com
http://google.scholar.com
http://nanotechnologie.pagina.nl
ĆWICZENIA