UV absorbing compounds, compositions comprising same and uses thereof

A compound of formula I, or a salt thereof:

• wherein, R1 and R2 are independently selected from the group consisting of C1 to C10 alkyl and C2 to C10 alkenyl, each of which groups may be substituted or unsubstituted;
• R3 is selected from the group consisting of substituted or unsubstituted C1 to C12 alkenyl and
• wherein R7 is selected from the group consisting of C1 to C20 alkyl, C2 to C20 alkenyl, C2 to C20 alkynyl, aryl, heteroaryl, heterocyclyl, aroyl, C2 to C20 alkanone, C5 to C7 cycloalkyl, C4 to C7 cycloalkanone, C2 to C12alkylalkanoate, C5 to C7 cycloalkenyl, C1 to C6 alkylcycloalkyl, C2 to C20 alkanoyl, C2 to C20 alkanoyloxy, C2 to C20 alkoxycarbonyl, C2 to C20 carbamoyl, C2 to C20 carboxyl, haloalkyl, N-alkyl, N-aryl, N-heterocyclyl, N—SO2—R30 and heterocyclic all of which groups may be substituted or unsubstituted and wherein R30 is selected from the group consisting of C1 to C6 alkyl and phenyl each of which may be substituted or unsubstituted, with the proviso that R3 comprises a carbon atom directly attached to the ring structure in formula I and that carbon is double bonded to another atom;
• R4 is selected from the group consisting of hydrogen, C1 to C12 alkyl, C2 to C12 alkenyl, aryl, heteroaryl, C5 to C7 cycloalkyl, C5 to C7 cycloalkenyl, C1 to C12 alkanoyl, C1 to C12 alkanoyloxy, C1 to C12 carboalkoxy and C1 to C12 alkanone all of which groups may be substituted or unsubstituted;
• R5 is selected from the group consisting of C1 to C12 alkyl, C2 to C12 alkenyl, C2 to C12 alkynyl, aryl, heteroaryl, heterocyclyl, C5 to C9 cycloalkyl, C5 to C7 cycloalkenyl, C2 to C9 alkanoyl, C2 to C9 alkanoyloxy and carbamoyl all of which groups may be substituted or unsubstituted;
• R6 is selected from the group consisting of hydrogen, oxo, substituted or unsubstituted C1 to C6 alkyl, substituted or unsubstituted C2 to C6 alkenyl and substituted or unsubstituted C2 to C6 alkanoyl;
• and
• R18 and R19 are independently selected from the group consisting of hydrogen, C1 to C6 alkyl, C2 to C6 alkenyl and C1 to C6 alkoxy, each of which groups may be substituted or unsubstituted,
• with the proviso that when R5 is alkyl or cycloalkyl and R4 is hydrogen then R7 is not an unsubstituted alkyl chain, an ester or an ether;
• and
• when R5 is unsubstituted benzyl then R7 is not hexyl;
• and wherein,
• the compound is not