There is provided a compound having Formula (I) R.sub.1-Z-R.sub.2 wherein R.sub.1 is a group selected from optionally substituted fused polycyclic groups, substituted alkyl groups, branched alkyl groups, and optionally substituted cycloalkyl groups Z is a linker which is or comprises a carbonyl group or a isostere of a carbonyl group R.sub.2 is selected from optionally substituted aromatic rings and optionally substituted heterocyclic rings wherein (a) R.sub.2 is a 2-substituted thiophene group, and/or (b) Z is a group of the formula --C(.dbd.O)--CR.sub.3R.sub.4--X--(CR.sub.5R.sub.6)n-, wherein X is selected from NR.sub.7, S, O, S.dbd.O, and S(.dbd.O).sub.2, wherein n is 0 or 1 and/or (c) R.sub.1 is an adamantyl group and Z is or comprises an amide group, and/or (d) R.sub.1 is an adamantyl group and Z is or comprises a group of the formula --(CR.sub.8R.sub.9)p-NR.sub.10--S(.dbd.O).sub.2--(CR.sub.11R.sub.12)q-, wherein p is 0 or 1 and q is 0 or 1 and/or (e) R.sub.1 is an adamantyl group and Z is or comprises a group of the formula --(CR.sub.13R.sub.14)V--Y--(CR.sub.15R.sub.16)W-- where Y is a heteroaryl group in which a bond in the heteroaryl ring is a isostere of a carbonyl group, wherein v is o or 1 and w is 0 or 1; wherein each of R.sub.3, R.sub.4, R.sub.5, R.sub.6, R.sub.8, R.sub.9, R.sub.11, R.sub.12, R.sub.13, R.sub.14, R.sub.15 and R.sub.16, are independently selected from H, hydrocarbyl and halogen, wherein each of R.sub.7 and R.sub.10 are independently selected from H and hydrocarbyl.