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27.10.04 ws 04/05-functional π-systems: part 1 1
ω Introduction: From colorants to functional dyes and beyondω Light, color, perception, absorption, reflection (transmission)ω Colorants, dyes, pigments – classification of dyes and pigmentsω Absorption, emission, spectra, excited statesω Structure-color relationshipω Natural dyesω Dye-based processes: Electron transfer, energy transferω Molecular electronicsω Photoinduced charge separation and thermally induced charge
recombination
WS 2004/2005: Functional π- systems, color anddyes: Overview and Topics (part I)
27.10.04 ws 04/05-functional π-systems: part 1 2
» H. R. Christen, F. Vögtle, Organische Chemie - Von den Grundlagen zurForschung, Vol. II, Vol. III, Otto Salle Verlag, Frankfurt am Main.
» E. Breitmaier, G. Jung, Organische Chemie: Grundlagen, Stoffklassen,Reaktionen, Konzepte, Molekülstruktur, 4th ed., Thieme, Stuttgart.
» H. Zollinger Colour Chemistry -Syntheses, Properties and Applications ofOrganic Dyes and Pigments, VCH, Weinheim.
» N. J. Turro, ‘Modern Molecular Photochemistry’, The Benjamin/CummingsPublishing Co., Menlo Park.
» M. Klessinger and J. Michl, ‘Excited States and Photochemistry of OrganicMolecules’, VCH, Weinheim.
» F. Vögtle, J. F. Stoddart, M. Shibasaki, Stimulating Concepts inChemistry, Wiley-VCH, Weinheim.
Books and articles
27.10.04 ws 04/05-functional π-systems: part 1 4
» M. Kollmannsberger, PhD thesis, Universität Regensburg,1999.
tmf
ε
0
8•104
λ (nm)500300
fluorescenceabsorption
B
NN
FF
high quantum yield ofemission
Spectral properties of dyes
27.10.04 ws 04/05-functional π-systems: part 1 5
R
CNCNH
SSR R
R = Phλmax = 350 nm
Photochromism: Dihydroaryl principle
27.10.04 ws 04/05-functional π-systems: part 1 6
NC
CN
H
CNCN
light
dark
DHA VHF
1
8a
9
10
Dihydroazulene Photochromism
27.10.04 ws 04/05-functional π-systems: part 1 7
» Chemie in unserer Zeit1999, 33, 72.
Reaction center of the bacterial photosynthesis(purple bacteria Rhodobacter)
27.10.04 ws 04/05-functional π-systems: part 1 8
» Nature 1998, 395, 583.
Solar cell - dye sensitized device
27.10.04 ws 04/05-functional π-systems: part 1 9
» Nature 1998, 395, 583.
photocurrent actionspectrum
3: dye-sensitizedheterojunction
Solar cell: actionspectrum
27.10.04 ws 04/05-functional π-systems: part 1 10
NH-Lysin-Protein+
11
"Retinal + Opsin"Rhodopsin
Solar light – vision – pigment of vision -incandescent bulb
27.10.04 ws 04/05-functional π-systems: part 1 11
» J. Griffiths, Chemie in unserer Zeit 1993, 27, 21.
increaseof energy
white light
Dispersion of white light
27.10.04 ws 04/05-functional π-systems: part 1 12
N
OHN
NaO3S O2N
dye 2.25
! Perception of the colorsin acidic solution: orangein basic solution: wine red
» H. Zollinger, Color Chemistry.
Structure, color, perception, media effect
27.10.04 ws 04/05-functional π-systems: part 1 13
∗ ε, molar absorptivity (molarextinction coefficient) in M-1 cm-1
(1000 cm2mol-1)∗ l, path length of the cell (in cm)∗ c, concentration [in moles per
liter (M)]
clIIE ××== ε0log
Lambert-Beer Law
27.10.04 ws 04/05-functional π-systems: part 1 14
Incoming color and reflected color
» H. Beyer, W. Walter, Lehrbuch der Organischen Chemie
27.10.04 ws 04/05-functional π-systems: part 1 15
W: neutral (white) pointpc = a/b: purity of the colorC: complementary color pointF: color pointdominant wavelength λD
Taken from Zollinger „ColorChemistry“
CIE chromaticity diagram
27.10.04 ws 04/05-functional π-systems: part 1 16
Colorants, dyes, pigments
Colorants (farbige Verbindungen):absorb or emit light in the visible range
(400 – 700 nm)
Dyes (functionalizedcolorants) are soluble(preferentially watersoluble) and colored
materials which can beimmobilized on substrates
Pigments are coloredparticles unsoluble in wateror other solvents in order to
make attachment onsubstrates auxiliary
materials have to be used
27.10.04 ws 04/05-functional π-systems: part 1 17
! Subunits of a colorant∗ chromophore∗ auxochromic group (donor group)∗ antiauxochromic group (acceptor group)
! Definition of a chromogen∗ Electron acceptor—chromophore — electron donator
n
acceptordonor
NMe
NMe
+
I-
pushpull
Color-structure relationship
cyanine dye
27.10.04 ws 04/05-functional π-systems: part 1 18
! Polyene and polymethine dyes∗ carotinoids∗ cyanine, hemicyanine, streptocyanine, oxonol
! Tri(di)arylmethine dyes∗ malachite green, crystal violet, phthaleins, xanthenes,
(phenolphthalein), azines, methylene blue
! Aza[18]annulenes∗ porphyrines, porphins, corrins, phthalocyanines∗ open-chain tetrapyrrols
Classification of dyes - I
27.10.04 ws 04/05-functional π-systems: part 1 19
O
Ethen, λmax(nm) = 180 nm 2,4,6,8-Decatetraen, λmax(nm) = 310 nm
2,4,6,8,10-Dodecapentaen, λmax(nm) = 340 nm
β-Carotin, λmax(nm) = 450 nm, orange
Retinal (Vitamin A-Aldehyd), λmax(nm) = 360 nm
Polyenes
27.10.04 ws 04/05-functional π-systems: part 1 20
N NH
NNH
N NH
NNH
N
N N
N
H
A B
CD
A B
CD
A B
CD
porphyrin chlorin corrin
Aza[18]annulenes: Porphyrin, chlorin, corrin
27.10.04 ws 04/05-functional π-systems: part 1 21
Aza[18]annulenes: (Metal)Phthalocyanines
N N
NNM
M: metal ion, Cu2+, Ni2+, etc.
absorption spectra:Q band: 650-730 nmB band: 320-340 nm
broken line (---): Ni-phthalocyanine
taken from Zollinger, Color Chemistry
27.10.04 ws 04/05-functional π-systems: part 1 22
! Azo dyes and pigments∗ methyl orange, and others
! Carbonyl dyes and pigments∗ indigo, anthraquinone dyes, quinacridones, alizarine,
diketo-pyrrolo-pyrrole and others
Classification of dyes - II
27.10.04 ws 04/05-functional π-systems: part 1 23
Azo dyes for reactive dyeing of cellulosic fibers
N N
N
N
N
N
NN
NHNH
N
SO3H
O
HO3S SO3HCl
HO3S SO3H
O H
HO3S
Cl
H
N
C.I. Reactive Red 120
C.I.: color index)
27.10.04 ws 04/05-functional π-systems: part 1 24
Diketo-pyrrolo-pyrrole (DPP) dyes
NH NH
O
O
pentalene
3,6 Diphenyl-2,5-dihydro-pyrrolo[3,4-c]pyrrole-1,4-dione
• red, high-melting pigment• applications: automotive
paints, coloring of plastics,printing ink
• molecular electronicssolid line: in DMSOdotted line: in the solid state
27.10.04 ws 04/05-functional π-systems: part 1 25
• intensity of an allowed transition:εmax ~ 104 – 105
• energy of excitation:(Ea)/kcal mol-1 = 28 600/λ (nm)
• life time of the excited state:ke° ≡ 1/τo ∼ 104 εmax (sec-1) (onlyradiative processes considered)
400 nm 700 nm
"NIR Farbstoffe""UV-Farbstoffe"
Wellenlänge
Absorption band and excited state properties
27.10.04 ws 04/05-functional π-systems: part 1 26
! approximate rates ofground state and excitedstate processeslight absorption: 1015 s-1
vibrational relaxation: >1012 s-1
fluorescence: 106 to 109 s-1
intersystem crossing: 10-1 to 105
s-1
phosphorescence: 10-2 to 104 s-1
Jablonski diagram
27.10.04 ws 04/05-functional π-systems: part 1 27
Radiative lifetime: τ0 ≈ 10-4/εmax
a weak absorption corresponds to alonger lifetime of the excited state
» J. Chem. Ed. 1998, 75, 615.
∗ S0 → S1 ~340 nm (weakband)
∗ S0 → S2 ≈ 335 nm (intenseband)
∗ lifetime of the excited state(S1): 382 ns
Absorption spectrum of atypical π-system: Pyrene
27.10.04 ws 04/05-functional π-systems: part 1 28
Properties of the excited state∗ Excimer formation at higher
concentration∗ fluorescence of the S1 state
(excited monomer) is structuredunlike the excimer emission
∗ other relaxation processes fromS1: S1 → T1 (efficiency about 38 %in ethanol)
Pyrene emission spectra as afunction of concentration (inhexane)
Supramolecular chemistry of the excited stateof pyrene: Monomer and excimer emission
monomer
excimer
27.10.04 ws 04/05-functional π-systems: part 1 29
Pyrene: Energy surfaces of the ground stateand excited state
27.10.04 ws 04/05-functional π-systems: part 1 30
FDY/LU
FDY/LU
! B. Valeur, Molecular Fluorescence, Wiley-VCH,Weinheim, 2002.
! B. M. Krasovitskii, B. M. Bolotin, Organic LuminescentMaterials, VCH, Weinheim, 1988.
Luminescence and luminescent materials
27.10.04 ws 04/05-functional π-systems: part 1 31
FDY/LU
OHO
CO2
OHO
CO2
O
M+M+
fluoresceinfluorescent
phenolphtaleinnon-fluorescent
Fluorescent and non-fluorescent dyes - I
27.10.04 ws 04/05-functional π-systems: part 1 32
FDY/LU
N N
H
H
Ph Ph
H
HPhPh
1,4-diphenylbutadienefluorescent
dibenzalazinenon-fluorescent
N+
NB
FF
N NH
-
boradiazaindacenefluorescent
dipyrromethenenon-fluorescent
O
NNPhPh
2,5-diphenyl-1,3,4-oxadiazolefluorescent
Fluorescent and non-fluorescent dyes - II
27.10.04 ws 04/05-functional π-systems: part 1 33
ON O
RX
N
O
OH2N
H NH
-O3S
CH3
O
CO2HBr
OHBr
Br
BrO
O
N
CH3
CNNC
CH3
CH3
Eosin Y DCM
C480: R=CH3, X=HC343: R=H, X=COO-C153: R=CF3, X=H
4AP TNS
∗ Dipole moment nearlyzero in the groundstate
∗ Dipol moment is largein the excited state
∗ time dependentfluorescent Stokesshift (TDFSS)
! Acc. Chem. Res. 2003, 36, 95. FDY/LU
Fluorescent dyes: Solvation Dynamics and ProtonTransfer in Supramolecular Assemblies
27.10.04 ws 04/05-functional π-systems: part 1 34
O
O
NH
H O
O
N CH3H
N MeMe
NMe2Me2N
N
S NMe2Me2N
2-aminoanthraquinone (A) 1-methylamino-anthraquinone (B)
+Cl-
crystal violet (C)
+
methylene blue (D)
Structure-color relationship - I
27.10.04 ws 04/05-functional π-systems: part 1 36
NN
H
H
(E)-Azobenzene (E)-Stilbene
N
H
N
MeMe
Benzylideneaniline
Indolenine
(twisted around C-N)
(planar; λmax = 310/235 nm)
» taken from Zollinger„Color Chemistry“
Structure-color relationship III:Similarity of absorption spectra of different chromophores
27.10.04 ws 04/05-functional π-systems: part 1 37
Structure-color relationship IV: Pigments absorbing inthe visible region of the spectrum
» Pure Appl. Chem. 1996, 68, 1373.
27.10.04 ws 04/05-functional π-systems: part 1 38
! Pure Appl. Chem. 1996, 68, 1373.
Structure-color relationship V: Spectral parameters
27.10.04 ws 04/05-functional π-systems: part 1 39
∗ Chlorophylls have two absorption bands, one in the red one in the blue∗ Phycoerythrins absorb blue and green light∗ Phycocyanins absorb yellow light
» D. Voet, J.G. Voet,Biochemistry, Wiley,New York,1995
Natural dyes - I: Photosynthesis
27.10.04 ws 04/05-functional π-systems: part 1 40
O
OH
OH
OH
OHR
R
aglycon (anthocyanidin);sugars are bound at O-3 and O-5
35
7
4'+
! F. Pina, M. J. Melo, MT. Goto, T. Kondo, Angew. Chem. 1991, 103, 17.
∗ widely distributed throughthe plant kingdom
∗ colours reaching fromsalmon, pink, scarlet,magenta, violet to blue.
∗ molecular stackingphenomena, hydrogenbonding
! flavonoids and anthocyanins
O
O
O
flavon flavylium cation
+
Natural dyes II: flowers
27.10.04 ws 04/05-functional π-systems: part 1 41
kET
» M. N. Paddon-Row. Electron and Energy Transfer. In Stimulating Concepts inChemistry; Vögtle, F.; Stoddart, J. F.; Shibasaki, M. Eds.; Wiley-VCH,Weinheim, 2000; pp. 267-291.
kET ∼ e-ßr
r: distancebetween D and Aß: damping factor
D-A → D+-A-(charge separation)
λ: reorganization energy
Basic processes of dyes:electron transfer (ET)
donor-bridge-acceptor
27.10.04 ws 04/05-functional π-systems: part 1 42
» R. A. Marcus, Angew. Chem. 1993, 105, 1161-1280.
!normal and inverted region
reaction coordinate
Marcus theory
27.10.04 ws 04/05-functional π-systems: part 1 43
2
14
°∆+=∆ ∗
λλ GG
TkG
ETBeAk∗∆
−
⋅=
! R. A. Marcus, Angew.Chem. 1993, 105, 1161-1280.
Electron transfer:normal andinverted region
27.10.04 ws 04/05-functional π-systems: part 1 44
» J. R. Miller, L. T. Calcaterra, G. L. Closs, J.Am. Chem. Soc. 1984, 106, 3047-3049.
!puls radiation studies(solvated electrons)
Experimental proof of the Marcus-inverted region
27.10.04 ws 04/05-functional π-systems: part 1 45
» M. N. Paddon-Row. Electronand Energy Transfer. InStimulating Concepts inChemistry; Vögtle, F.;Stoddart, J. F.; Shibasaki, M.Eds.; Wiley-VCH: Weinheim,2000; pp. 267-291.
∗ Electronic excitationenergy transfer (EET)
rate ~ 1/r6
rate ~ e-r
Basic processes of energytransfer: Excitation energytransfer (EET)
27.10.04 ws 04/05-functional π-systems: part 1 46
» J. M. Tour, inStimulating Concepts inChemistry (Eds.: F.Vögtle, J. F. Stoddart,M. Shibasaki), Wiley-VCH, Weinheim, 2000,pp. 237-253.
∗ Molecular Diodes
Components of molecular electronics
27.10.04 ws 04/05-functional π-systems: part 1 47
» J. Am. Chem. Soc. 1996, 118, 6767.
∗ Generation of long lived charge separation in the excited state:quantum yield 0.92, energy storage ~2 eV, life time 300 ns
N NN N N C8H17
O
O
O
O
O
OMeO
Energy conversion (energy storage): Photoinducedcharge separation
27.10.04 ws 04/05-functional π-systems: part 1 48
» M. N. Paddon-Row, in StimulatingConcepts in Chemistry, 2000, pp.267.
Photosynthesis and charge separation