Abstract: A porphycene having the structure ##STR1## wherein each R.sup.1 is, independently, (a) --(CH.sub.2).sub.n --X, where n=1-4, X is OR.sup.2 and R.sup.2 is C.sub.1-6 alkyl, aralkyl or aryl; CN; OH; OSO.sub.2 R.sup.2 ; NH.sub.2 ; NHR.sup.2 ; NR.sub.2.sup.2 ; SH; SR.sup.2 ; S(O).sub.1-2 R.sup.2 ; COOH; CO.sub.2 R.sup.2 ; C(O)NH.sub.2 ; C(O)NHR.sup.2 ; C(O)NR.sub.2.sup.2 ; halogen; or CHO;(b) --(CH.sub.2).sub.m CH.dbd.CH.sub.2 where m is 0-2; or(c) --(CH.sub.2).sub.n --O--G where G is a mono- or oligosaccharide;(d) --(CH.sub.2).sub.2n --X, where X is an amino acid, oligopeptide covalently bonded by an ether-, ester- or amine-bond or --Y-- (CH.sub.2).sub.n -porphycene.sup.2 (porphycene.sup.2 being a compound of the same structure and Y is a direct bond; --O--; or --CH.dbd.CH.sub.2); or(e) where one, two or three of the substituents R.sup.1 are C.sub.1-6 alkyl or aryl and the remaining substituents are as above under (a)-(d), and salts and metal complexes thereof.