Oxygen sensors

A compound of Formula I:

• wherein M is H, Pd, Zn, Pt, Gd, or Yb;
• each R1 is same or different and, independently, C(O)X—(CH2)n—YC(O)C(R4)CH2 or C(O)X—(CH2CH2O)mCH2CH2—YC(O)C(R4)CH2;
• R7 is C(O)X—(CH2)n—YC(O)C(R4)CH2, C(O)X—(CH2CH2O)CH2CH2—YC(O)C(R4)CH2;
• R2 and R3 are fused, in each case, to form a cycloalkenyl, aryl, or heteroaryl group;
• X is O or NR5;
• Y is O;
• R5 and R4 are independently H or C1-C4 alkyl;
• each R6 is same or different and, independently, H or F;
• n is 1-10;
• and
• m is 1-300.