Merocyanine Merocyanine dyesdyes

Synthesis, properties, applicationSynthesis, properties, application

Eugenij Poronik

2

IntroductionIntroduction

• Merocyanine dyes are considered as a superposition of neutral (I) and zwitterionic (III) forms.• There is an ideal state, so-called “cyanine limit”, which relates to equal contributions of the polyene-type and the

zwitterionic resonance structures.• Merocyanines in the cyanine limit are also dyes with most favorable absorption properties, that is, intense

absorption bands at the longest possible wavelength for a given polymethine chain, and they possess enhanced thermal and photochemical stability owing to equalized bond orders

D AnD An

D An

I II III

N

O

N

O

NaO3S

N

N

O

O

S

Brooker’s merocyanine

Merocyanine 540

N

O

N

O

J Am Chem Soc 73 (1951) 5326

3

Simple Merocyanines (n = 0)

SynthesisSynthesis

Zeromethine merocyanines (n = 0) are commonly prepared by the reaction of nitrogen heterocycles containing a leaving group with active methylene bases.

J Am Chem Soc 73 (1951) 5326

Bull Korean Chem Soc 24 (2003) 569

87%

50%

4

J Chem Soc, Perkin Trans 2 (1997) 1055

Tetr. Lett 39 (1998) 1763

5

Merocarbocyanines (n = 1)

The classical route for the synthesis of merocarbocyanine dyes is a reaction of heterocyclic enamines or corresponding salts with hydroxybenzaldehydes or their heterocyclic analogs.

Russ Chem Bull, Int Ed 54 (2005) 2417

Dyes Pigm 60 (2004) 215Dyes Pigm 58 (2003) 83

J Mater Chem 9 (1999) 2991

6

Dyes Pigm 58 (2003) 83

The capability of merocyanines to produce salts is used for their isolation

N

OH

OTs

NaBF4

N

OH

BF4

N

ONaOH

crude in water soution pure precipitate pure

7

A versatile method for the preparation of merocyanine dyes involves the treatment of methyl-substituted quaternary salts of nitrogen heterocycles with anilinomethylene derivatives of heterocyclic ketones.

Using of aldehyde analogousUsing of aldehyde analogous

O O

NH

Ph

PhN=CHOEt

Het Het

8

Acetanilidomethylene-substituted heterocycles are useful, versatile synthones, and they have been extensively used for the preparation of merocyanine dyes

9

Dimethylaminomethylene derivatives prepared by treatment of carbo and heterocyclic ketones with DMF-DMA or with DMF in acetic anhydride have been used for the synthesis of various merocyanine dyes

10

This reaction is suitable for the preparation of symmetrical merocyanines (ketocyanines), difunctionalized ketones are condensed with two equivalents of quaternary salt

O

N

XX

N

Et Et

RR

X = C(CH3)2, S; R = H, OH, COOEt, NHAc, benzo Tetr. Lett. 42 (2001) 6129

Russ Chem Bull 45 (1996) 164

11

From -aldehydes

The condensation of -aldehydes with active methylene compounds in in the absence of the base leads to merocyanines in moderate yields

Org Lett 5 (2003) 3143Angew Chem Int Ed 36 (1997) 2765

Aza derivatives of -aldehydes are the most utilized starting materials for the preparation of merocyanine dyes since the first merocyanine syntheses

J Am Chem Soc 121 (1999) 8146

12

A versatile one-pot synthesis of merocyanines based on multi-step reaction of nitrogen heterocycles with active methylene compounds and DMF in acetic anhydride [45, 59].

The process is uninfluenced by impurities in starting compounds, including water, and can be used in combinatorial synthesis.

Synthesis (1999) 2103Angew Chem Int Ed 38 (1999) 1649

13

Tetrahedron 55 (1999)14421

51%

NH

NH

O

OHC CHO

O

HN

O

32%

EtOH/HCl

14

NN

Et Et

RR

O

NN

Et Et

RR

Cl

N

O

O

O-K+ DMF

X

Heterocycl Commun 11 (2005) 129

15

Long-Bridge MerocyaninesLong-Bridge Merocyanines

Similar methodology as utilized for the synthesis of simple merocyanines is useful for the preparation of their cyclic higher vinilogues.

J Chem Soc, Faraday Trans 93 (1997) 3653

16

J Appl Spectroscopy 71(2004) 641

17

Structure and IsomerizationStructure and Isomerization

• Merocarbocyanines can exist as four transoid isomers with regard to two double bonds of the bridge fragment.

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SolvatochromismSolvatochromism

Solvatochromic merocyanines exhibit bathochromic or hypsochromic shifts in solvents of various polarities. Other characteristics such as dipole moments, fluorescence, and NLO properties change as well.

Acetone, 96 % ethanol, acetic acid, water, DMF, acetonitrile, 2-propanol, methanol, THF and DMSO

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O

N

O

H3CO NEt2

Titration with Ni2+

Ion SensorsIon Sensors

20

Anal Chim Acta 504 (2004) 227

Calcium-sensitive chromogenic crown ethers. The water-soluble dye (R = CH3) can be used for calcium ion sensing in solution while lipophilized derivative (R = C12H25) has been successfully applied to ion-exchange type optode PVC membranes.

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Molecular AggregationMolecular Aggregation

Molecular aggregates are self-assemblies of molecules by non-covalent interactions. They have significant technological applications such as molecular optoelectronic devices,

fluorescence probes for mitochondrial membrane, and as models of antenna systems that function to transfer energy and electrons in biological systems

22

Langmuir 20 (2004) 5718-5723

Aggregation processes of merocyanine dyes on lyposomes (artificial cellAggregation processes of merocyanine dyes on lyposomes (artificial cell membranes)membranes)

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SpiropyransSpiropyrans

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3D d3D data storage mediaata storage media

Schematic representation of a cross-section through a 3D optical storage disc (yellow) along a data track (orange marks). Four data layers are seen, with the laser currently addressing the third from the top. The laser passes through the first two layers and only interacts with the third, since here the light is at a high intensity.

No commercial product based on 3D optical data storage has yet arrived on the mass market, althoughseveral companies are actively developing the technology and claim that it may become available "soon".

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Photodynamic therapyPhotodynamic therapy

J Photochem Photobiol B 32 (1996) 27-32

N

O

NaO3S

N

N

O

O

S Merocyanine 540

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Non-linear properties

NCN

CN

N

N

N

O O

N

N

PhN

N

O

O O

Ph

N

N

Ph

CN

CN

Ph

O

= 115 GM

= 35 GM

= 25 GM

= 125 GM

Optics Commun 281 (2008) 6072-6079at 1064 nm

27

O

O O

O

N

B

F F

n

N

nmax = 2300 GM (at 826 nm)

n = 2; max = 5000 GM (at 900 nm)

n = 3; max = 10000 GM (at 980 nm)

J. Mater. Chem. 19 (2009) 7503–7513

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Merocyanine dyes with nitrogen donor and carbonyl acceptor fragments have found a wide application in various areas of science and technology, including optical and fluorescent sensors, silver halide photography, optical data storage, and photodynamic therapy.

The synthetic methods on merocyanines preparation allow to obtain dyes with a wide variety of electron donor and acceptor parts, and hence with various properties.

Recent progress in computer science and nanotechnology have stimulated new investigations, including the studies in non-linear optics, and new areas of medicine.

ConclusionsConclusions

Thank you for your attention