Abstract: The present invention provides a porphyrin derivative having improved water solubility, desirably having both water solubility and lipophilicity. Specifically, the present invention provides a water-soluble porphyrin consisting of a tetraphenylporphyrin derivative represented by Formula (1): wherein m represents an integer of 1 to 30; n represents an integer of 2 to 4; R represents a hydrogen atom or an optionally substituted alkyl or aromatic group; Ph represents an optionally substituted phenyl group; and X? is a counterion and represents a halide ion, PF6?, or BF4?.

Abstract: The present invention provides a porphyrin derivative having improved water solubility, desirably having both water solubility and lipophilicity. Specifically, the present invention provides a water-soluble porphyrin consisting of a tetraphenylporphyrin derivative represented by Formula (1): wherein m represents an integer of 1 to 30; n represents an integer of 2 to 4; R represents a hydrogen atom or an optionally substituted alkyl or aromatic group; Ph represents an optionally substituted phenyl group; and X? is a counterion and represents a halide ion, PF6?, or BF4?.

Abstract: A novel organic ultrathin membrane characterized in that an amphiphilic compound having a pigment group and a nucleic acid base is aligned due to base-pairing with an oligonucleotide which is capable of forming a base pair with the nucleic acid base to thereby constitute a monolayer is provided. In this organic ultrathin membrane, free space is provided around a pigment molecule so as to enable photoisomerization of the pigment molecule in a high-density solid state. Thus, it is useful as an optical memory, etc. Further, a process for producing the organic ultrathin membrane is provided.