Abstract: Compounds having utility as light absorbing compounds, especially in the area of photodynamic therapy. Such compounds have the formula: ##STR1## where z is .dbd.O or NR.sub.14 ; R.sub.14 is alkyl or substituted alkyl; R.sub.1 is an amino acid group, a polyamine group, a polyether group or OR.sub.13 where R.sub.13 is alkyl; R.sub.4 through R.sub.11 are --H, --OH alkyl, alkoxy, alkenyl, alkylene, aryl, or aryloxy, or a carbonyl containing group, wherein carbon containing groups may be substituted with carbonyl, hydroxy, phosphoro, carboxy, halo, sulfo, amino and ether substituents, provided that; R.sub.4 may be taken together with R.sub.7 to form .dbd.O; R.sub.8 may be taken together with R.sub.9 to form .dbd.O; R.sub.10 may be taken together with R.sub.11 to form .dbd.O; and R.sub.4 and R.sub.7 may together form a chemical bond and R.sub.8 and R.sub.11 may together form a chemical bond; and R.sub.12 is hydrogen or lower alkyl; provided that if one z is O, the other z is --NR.sub.14.

Abstract: A method for the preparation of an imide derivative of purpurin by reacting hexylamine with a chlorin or bacteriochlorin having a macrocycle with a six-membered anhydride ring fused thereto, said macrocycle containing a and b rings which may be saturated or unsaturated at R.sub.4 to R.sub.11 positions of the rings and which R.sub.4 and R.sub.11, positions may contain at least one group selected from the group consisting of hydrogen, hydroxy, formyl, substituted and unsubstituted alkyl, alkoxy, alkenyl, aryl and aryloxy wherein carbon containing groups may be substituted with a substituent selected from, hydroxy, phosphoro, carboxy, halo, sulfo, amino and ether, to obtain a purpurin derivative; and reacting the purpurin derivative with a carbodiimide to obtain the imide derivative of purpurin. The invention further includes novel imides made by the method.