Phosphine oxide-based photoinitiators

A precursor of formula (30) or (31):

• wherein
• each Ar is independently an optionally substituted arylene;
• R1 and R2 are independently H or an optionally substituted group selected from alkyl and aryl;
• or R1 and R2, together with the carbon atoms to which they are attached, form a ring;
• each R3 is independently an optionally substituted group selected from alkyl, aryl and alkoxy;
• Q1 is an optionally substituted aryl or a group of formula (3):
• wherein:
• each Ra is independently an optionally substituted group selected from alkyl, aryl, alkoxy, aryloxy, thioalkyl and thioaryl;
• and
• y is a number chosen from 0 to 5;
• Q2 and Q3 are independently —OR14, —SR15, —NR16R17, —O—[CH2—CH(OH)—Y1]a—Z1, —S—Z2, —N(R18)—Z3 or —O-Cyhex-Y2—Z4;
• or Q2 and R′1, together with the atoms to which they are attached, form a 5-7 membered ring;
• or Q3 and R′1, together with the atoms to which they are attached, form a 5-7 membered ring;
• R14 and R15 are independently H or an optionally substituted group selected from alkyl, cycloalkyl, heterocycloalkyl, aryl and heteroaryl;
• R16, R17 and R18 are independently H, or an optionally substituted group selected from alkyl and aryl;
• or R16 and R17, together with the nitrogen atom to which they are attached, form a 5-7 membered ring;
• Cyhex is a cycloyhexylene substituted by a hydroxyl group, preferably represented by the following formula:
• Y1 is a bond, —CH2—O—* or —CH2—C(═O)—O—*;
• Y2 is a bond, —CH2—O—C(═O))-# or —C(═O)—O—#;
• a is 0 or 1;
• Z1, Z2, Z3 and Z4 are independently a phosphine oxide-containing moiety;
• the symbol * represents a point of attachment to moiety Z1;
• the symbol # represents a point of attachment to moiety Z4.

A precursor of formula (33) or (34)

• wherein:
• each Ar is independently an optionally substituted arylene;
• R1 and R2 are independently H or an optionally substituted group selected from alkyl and aryl;
• or R1 and R2, together with the carbon atoms to which they are attached, form a ring;
• each R3 is independently an optionally substituted group selected from alkyl, aryl and alkoxy;
• Q1 is an optionally substituted aryl or a group of formula (3):
• wherein:
• each Ra is independently an optionally substituted group selected from alkyl, aryl, alkoxy, aryloxy, thioalkyl and thioaryl;
• and
• y is a number chosen from 0 to 5;
• G is OH, a halogen atom or —O—C(═O)-J;
• J is alkyl or aryl.

A precursor of formula (52) or (53):

• wherein:
• each Ar is independently an optionally substituted arylene;
• R1 and R2 are independently H or an optionally substituted group selected from alkyl and aryl;
• or R1 and R2, together with the carbon atoms to which they are attached, form a ring;
• each R3 is independently an optionally substituted group selected from alkyl, aryl and alkoxy;
• one of R′1 and R′2 is H and the other of R′1 and R′2 is selected from —OR4, —SR5, —NR6R7, —C(R8)(CO—W1—R9)(CO—W2—R10), —C(R11)(CO—W3—R12)(CN) and —C(R13)(CN)2;
• or R′2 is H and R′1 and Q2, together with the atoms to which they are attached, form a 5-7 membered ring;
• or R′2 is H and R′1 and Q3, together with the atoms to which they are attached, form a 5-8 membered ring;
• Q1 is an optionally substituted aryl or a group of formula (3):
• wherein:
• each Ra is independently an optionally substituted group selected from alkyl, aryl, alkoxy, aryloxy, thioalkyl and thioaryl;
• and
• y is a number chosen from 0 to 5;
• G is OH, a halogen atom or —O—C(═O)-J;
• J is alkyl or aryl.