1. Merocyanine dyes Synthesis, properties, application
Eugenij Poronik

2. Introduction Brooker’s merocyanine J Am Chem Soc 73 (1951) 5326
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

3. Simple Merocyanines (n = 0)
Synthesis
Simple Merocyanines (n = 0)
87%
J Am Chem Soc 73 (1951) 5326
50%
Bull Korean Chem Soc 24 (2003) 569
Zeromethine merocyanines (n = 0) are commonly prepared by the reaction of nitrogen heterocycles containing a leaving group with active methylene bases.

4. J Chem Soc, Perkin Trans 2 (1997) 1055
Tetr. Lett 39 (1998) 1763

5. Merocarbocyanines (n = 1)
Russ Chem Bull, Int Ed 54 (2005) 2417
Dyes Pigm 60 (2004) 215
Dyes Pigm 58 (2003) 83
J Mater Chem 9 (1999) 2991
The classical route for the synthesis of merocarbocyanine dyes is a reaction of heterocyclic enamines or corresponding salts with hydroxybenzaldehydes or their heterocyclic analogs.

6. Dyes Pigm 58 (2003) 83
The capability of merocyanines to produce salts is used for their isolation

7. Using of aldehyde analogous
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.

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. Tetr. Lett. 42 (2001) 6129
This reaction is suitable for the preparation of symmetrical merocyanines (ketocyanines), difunctionalized ketones are condensed with two equivalents of quaternary salt
Russ Chem Bull 45 (1996) 164

11. From w-aldehydes Org Lett 5 (2003) 3143
Angew Chem Int Ed 36 (1997) 2765
The condensation of w-aldehydes with active methylene compounds in in the absence of the base leads to merocyanines in moderate yields
J Am Chem Soc 121 (1999) 8146
Aza derivatives of w-aldehydes are the most utilized starting materials for the preparation of merocyanine dyes since the first merocyanine syntheses

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

13. 51%
Tetrahedron 55 (1999)14421

14. Heterocycl Commun 11 (2005) 129

15. Long-Bridge Merocyanines
J Chem Soc, Faraday Trans 93 (1997) 3653
Similar methodology as utilized for the synthesis of simple merocyanines is useful for the preparation of their cyclic higher vinilogues.

16. J Appl Spectroscopy 71(2004) 641

17. Structure and Isomerization
Merocarbocyanines can exist as four transoid isomers with regard to two double bonds of the bridge fragment.

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

19. Ion Sensors
Titration with Ni2+

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.

21. Molecular 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)
Aggregation processes of merocyanine dyes on lyposomes (artificial cell membranes)

23. Spiropyrans

24. 3D data 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, although
several companies are actively developing the technology and claim that it may become available "soon".

25. Photodynamic therapy Merocyanine 540
J Photochem Photobiol B 32 (1996) 27-32

26. Non-linear properties
d = 115 GM
d = 25 GM
d = 35 GM
d = 125 GM
at 1064 nm
Optics Commun 281 (2008)

27. n = 1; dmax = 2300 GM (at 826 nm)
n = 2; dmax = 5000 GM (at 900 nm)
n = 3; dmax = GM (at 980 nm)
J. Mater. Chem. 19 (2009) 7503–7513

28. Conclusions
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.

29. Thank you for your attention