Abstract: A method for synthesizing a porphocyanine having the formula: ##STR1## where each R is ethyl, comprises either: (1) treating 3,3'-4,4'-tetraethyl-5,5'-bisaminomethyl-2,2'-dipyrromethane with a 10-fold excess of DDQ or(2) treating 3,3'-4,4'-tetraethyl-5,5'-diformyl 2,2'-dipyrromethane with ammonia, followed by column chromatography purification and evaporating to dryness the eluant containing the purified product.

Abstract: A group of novel expanded porphyrin-like compounds, porphacyanine (Pc) and porphacyanine-like compounds, having absorption maxima in the range of 400-850 nanometers is useful in detecting and treating targeted tissues, cells and viruses. The use of the Pc of the invention permits the irradiation to comprise wavelengths other than those absorbed by blood. The Pc of the invention may also be conjugated to target-specific moieties such as immunoglobulins or fragments thereof to target specific tissues or cells for the radiation treatment. Use of these materials permits greater depth of treatment penetration and greater specificity in targeting tissues or cells. Coupled with an appropriate paramagnetic ion or radioisotope, the Pc of the invention is suitable for use in nuclear magnetic resonance imaging and radioimaging.