Sulphide sensor

A compound having a structure according to Formula I, shown below:

• wherein
• each X is independently I or Br;
• each ring A is independently:
• i) an electron deficient 5- or 6-membered nitrogen-containing heteroaryl that is optionally substituted with one or more groups Re, where each Re is independently selected from (1-6C)alkyl, oxygen and aryl;
• or
• ii) a phenyl that is substituted with one or more groups Rf, where each Rf is an electron withdrawing group;
• each L is independently absent (such that ring A is directly bound to Y2) or a π-conjugated linker that separates ring A from Y2 by a distance of 4 atoms or fewer;
• Y1 is absent or is a fluorophore comprising coumarin or BODIPY;
• Y2 is absent or is a fluorophore comprising coumarin or BODIPY;
• B is a backbone group of the following structure:
• wherein denotes the point of attachment to each ring A;
• and
• i) R1, R2, R3 and R4 are independently selected from hydrogen, halo, hydroxy, (1-4C)alkyl, (2-4C)alkenyl, (2-4C)alkynyl, (1-4C)haloalkyl and (1-4C)alkoxy;
• and
• Q is selected from CRaRb, N+RaRb and NRc, where Ra, Rb and Re are each independently hydrogen, (1-6C)alkyl or aryl;
• or
• ii) R1 and R4 are absent, and R2 and R3 are linked to one another, such that when taken in combination with the atoms to which they are attached, they form a 5- or 6-membered heteroaryl or an aryl that is optionally substituted with one or more groups Ra, where each Rd is independently selected from halo, hydroxy, nitro, cyano, (1-6C)alkyl, (2-6C)alkenyl, (2-6C)alkynyl, (1-6C)haloalkyl, (1-6C)alkoxy, —NRd1Rd2, —C(O)—Rd1, and —C(O)—ORd1, where Rd1 and Rd2 are each independently selected from hydrogen and (1-4C)alkyl;
• and
• Q is an atom in the 5- or 6-membered heteroaryl ring or the aryl ring;
• with the proviso that Y1 and Y2 are not both absent;
• and
• wherein the compound of Formula I is substituted with one or more water solubilising groups, Z.