A transition metal complex represented by formula (I') or a salt thereof; wherein: X is Pt; n is an integer from 2 to 6; each R 1 is independently selected from halogen, NR'R"R"' (where each of R', R", and R'" is independently selected from hydrogen, C 1 to C 10 alkyl, C 3 to C 11 cycloalkyl, C 6 to C 14 aryl, C 2 to C 10 heteroaryl, C 1 to C 8 heterocyclyl and oxyacyl), optionally substituted acyloxy, optionally substituted C 1 to C 10 alkyl-O-, SR'R" (where each of R' and R" is independently selected from hydrogen, C 1 to C 10 alkyl, C 3 to C 11 cycloalkyl, C 6 to C 14 aryl, C 2 to C 10 heteroaryl, C 1 to C 8 heterocyclyl and oxyacyl), optionally substituted C 2 to C 10 heteroaryl, or any two R 1 form a malonate. oxalate or glycolate; R 2 is selected from optionally substituted C 1 to C 10 alkyl, optionally substituted C 2 to C 10 alkenyl, optionally substituted C 2 to C 10 alkynyl, optionally substituted C 6 to C 14 aryl, optionally substituted oxyacyl, optionally substituted acyl, optionally substituted aminoacyl. optionally substituted oxythioacyl, optionally substituted sulfinyl, optionally substituted sulfonyl, optionally substituted oxythioacyloxy, optionally substituted amino, optionally substituted aminothioacyl, and optionally substituted thioacyl; wherein "optionally substituted" is taken to mean that a group may or may not be further substituted or fused (so as to form a condensed polycyclic group) with one or more groups selected from hydroxyl, acyl, alkyl, alkoxy, alkenyl, alkenyloxy, alkynyl, alkynyloxy, amino, aminoacyl, thio, arylalkyl, arylalkoxy, aryl, aryloxy, carboxyl, acylamino, cyano, halogen, nitro, phosphono, sulfo, phosphorylamino, phosphinyl, heteroaryl, heteroaryloxy, heterocyclyl, heterocyclyloxy, oxyacyl, oxime. oxime ether, hydrazone, oxyacylamino, oxysulfonylamino, aminoacyloxy, trihalomethyl, trialkylsilyl, pentafluoroethyl, trifluoromethoxy, difluoromethoxy, trifluoromethanethio, trifluoroethenyl, mono- and di-alkylamino, mono-and di-(substituted alkyl)amino, mono- and di-arylamino, mono- and di-heteroarylamino, mono- and di-heterocyclyl amino, and unsymmetric di-substituted amines having different substituents selected from alkyl, aryl, heteroaryl and heterocyclyl; R 3 -R 8 are H; and R 11 -R 14 are independently selected from H or halogen. X is Pt; n is an integer from 2 to 6; each R 1 is independently selected from halogen, NR'R"R"' (where each of R', R", and R'" is independently selected from hydrogen, C 1 to C 10 alkyl, C 3 to C 11 cycloalkyl, C 6 to C 14 aryl, C 2 to C 10 heteroaryl, C 1 to C 8 heterocyclyl and oxyacyl), optionally substituted acyloxy, optionally substituted C 1 to C 10 alkyl-O-, SR'R" (where each of R' and R" is independently selected from hydrogen, C 1 to C 10 alkyl, C 3 to C 11 cycloalkyl, C 6 to C 14 aryl, C 2 to C 10 heteroaryl, C 1 to C 8 heterocyclyl and oxyacyl), optionally substituted C 2 to C 10 heteroaryl, or any two R 1 form a malonate. oxalate or glycolate; R 2 is selected from optionally substituted C 1 to C 10 alkyl, optionally substituted C 2 to C 10 alkenyl, optionally substituted C 2 to C 10 alkynyl, optionally substituted C 6 to C 14 aryl, optionally substituted oxyacyl, optionally substituted acyl, optionally substituted aminoacyl. optionally substituted oxythioacyl, optionally substituted sulfinyl, optionally substituted sulfonyl, optionally substituted oxythioacyloxy, optionally substituted amino, optionally substituted aminothioacyl, and optionally substituted thioacyl; wherein "optionally substituted" is taken to mean that a group may or may not be further substituted or fused (so as to form a condensed polycyclic group) with one or more groups selected from hydroxyl, acyl, alkyl, alkoxy, alkenyl, alkenyloxy, alkynyl, alkynyloxy, amino, aminoacyl, thio, arylalkyl, arylalkoxy, aryl, aryloxy, carboxyl, acylamino, cyano, halogen, nitro, phosphono, sulfo, phosphorylamino, phosphinyl, heteroaryl, heteroaryloxy, heterocyclyl, heterocyclyloxy, oxyacyl, oxime. oxime ether, hydrazone, oxyacylamino, oxysulfonylamino, aminoacyloxy, trihalomethyl, trialkylsilyl, pentafluoroethyl, trifluoromethoxy, difluoromethoxy, trifluoromethanethio, trifluoroethenyl, mono- and di-alkylamino, mono-and di-(substituted alkyl)amino, mono- and di-arylamino, mono- and di-heteroarylamino, mono- and di-heterocyclyl amino, and unsymmetric di-substituted amines having different substituents selected from alkyl, aryl, heteroaryl and heterocyclyl; R 3 -R 8 are H; and R 11 -R 14 are independently selected from H or halogen.