| abstract |
A robust compound is provided having the formula: wherein Y1, Y2, Y3 and Y4 are oxidation resistant groups which are the same or different and which form 5- or 6-membered rings with a metal, M, when bound to D. D is a metal complexing donor atom, O or N. Each X is a position for addition of a substituent and, when D is N, each position is (i) not occupied such that a double bond is formed between D and an atom adjacent to D, or (ii) is selected from the group consisting of hydrogen, alkyl, alkenyl, alkynyl, aryl, alkoxy, phenoxy, halogen, halogenated alkyl, halogenated aryl, halogenated alkenyl, halogenated alkynyl, perhaloalkyl, perhaloaryl, a substituted or unsubstituted cycloalkyl ring, a substituted or unsubstituted cycloalkenyl ring, a substituted or unsubstituted saturated heterocyclic ring, a substituted or unsubstituted unsaturated heterocyclic ring, and at least one X is hydrogen, and when D is O, the position is not occupied. |