in the ring backbone when the aryl is a ring system every ring in the system is aromatic the aryl group may have 6 to 18 carbon atoms although the present definition also covers the occurrence of the term u201c aryl u201d where no numerical range is designated in some embodiments the aryl group has 6 to 10 carbon atoms the aryl group may be designated as u201c c 6 10 aryl u201d u201c c 6 or c 10 aryl u201d or similar designations examples of aryl groups include but are not limited to phenyl naphthyl azulenyl and anthracenyl as used herein u201c aryloxy u201d and u201c arylthio u201d refers to ro u2014 and rs u2014 in which r is an aryl as is defined above such as u201c c 6 10 aryloxy u201d or u201c c 6 10 arylthio u201d and the like including but not limited to phenyloxy an u201c aralkyl u201d or u201c arylalkyl u201d is an aryl group connected as a substituent via an alkylene group such as u201c c 7 14 aralkyl u201d and the like including but not limited to benzyl 2 phenylethyl 3 phenylpropyl and naphthylalkyl in some cases the alkylene group is a lower alkylene group i e a c 1 4 alkylene group as used herein u201c heteroaryl u201d refers to an aromatic ring or ring system i e two or more fused rings that share two adjacent atoms that contain s one or more heteroatoms that is an element other than carbon including but not limited to nitrogen oxygen and sulfur in the ring backbone when the heteroaryl is a ring system every ring in the system is aromatic the.