Electrochromic compounds

This invention relates to novel electrochromic compounds. These compounds are useful in electrochromic devices such as electric windows, displays and other optical devices that can change colour according to the needs of the user. In particular, the compounds may be used in electrochromic devices comprising nanostructured films.

Viologen compounds, i.e. compounds which have a dipyridinium group and are capable of reversible reduction/colouration, are widely used in electrochromic devices. However, in conventional viologen-based systems, diners may be formed due to the parallel overlap of viologens, thereby preventing efficient decolouration in the electrochromic device.

It is an object of the invention to avoid or minimise the disadvantages of the prior art.

According to the present invention there are provided compounds of the general formula I

R¹ is —(CH₂)_m—wherein m is zero or an integer from 1 to 10; or aryl or heteroarl having up to 14 carbon atoms; or branched-chain alkyl or alkenyl, or cycloalkyl, each having up to 10 carbon atoms; the aryl, heteroaryl, branched alkyl branched alkenyl or cycloalkyl radical optionally being attached to the —P(O)(OH)₂ group via a —(C₂)_n-linkage, wherein n is zero or an integer from 1 to 10; it also being possible for the aryl, heteroaryl, branched alkyl, branched alkenyl or cycloalkyl radical to be optionally substituted by one or more of the following substituents which may be the same or different lower alkyl, lower alkenyl, phenyl-lower alkyl, diphenyl-lower alkyl, phenyl, phenoxy, lower alkanoyloxy, halogen, amino, cyano, nitro, lower alkylamino, di-lower alkylamino, phenylamino, lower alkanoylamino, benzoylamino; lower alkylsulfonylamino, phenysulfonylamino, lower alkanoyl, benzoyl, carboxy, lower alkoxycarbonyl, carbamoyl, N-lower alkylcarbamoyl, N,N-di-lower alkylcarbamoyl, ureido, N-lower alkylureido, lower alkylsulfonyl; phenyl sulfonyl; lower alkyl which is substituted by hydroxy, lower alkoxy, amino, lower alkylamino, di-lower alkylamino, halogen, carboxy or lower alkoxycarbonyl; lower alkoxy which is substituted by hydroxy, lower alkoxy, amino, lower alkylamino, di-lower alkylamino, halogen, carboxy or lower alkoxycarbonyl; C₃-C₇-alkoxy; and/or bivalent methylenedioxy; it being possible for all phenyl groups mentioned as such or in composed radicals (such as benzoyl, phenylamino etc.) to be unsubstituted or substituted by lower alkyl, lower alkoxy, halogen, hydroxy and/or nitro; and
R² is R³R⁴ wherein
R³ is —(CH₂)_p—wherein p is zero or an integer from 1 to 10; and
R⁴ is -P(O) (OH)₂; or aryl or heteroaryl having up to 14 carbon atoms; or branched-chain alkyl or alkenyl, or cycloalkyl, each having up to 10 carbon atoms, it being possible for the aryl, heteroaryl, branched alkyl, branched alkenyl or cycloalkyl radical to be unsubstituted or substituted by one or more of the substituents given in the definition of R¹; and
X is a charge-balancing ion;
with the provisos that R¹ cannot be —(CH₂)_m— wherein m is 2 or 3, when R² is —(CH₂)₂—P(O)(OH)₂; and R¹ cannot be —(CH₂)_m— wherein m is 2, when R² is phenyl.