Monomeric encapsulation of phthalocyanine‐dye molecules in the pores of Si‐MCM‐41 and Ti‐MCM‐41

Titanium species and substituted or unsubstituted zinc phthalocyanine (ZnPc) complexes exhibiting negative, positive or no charges are incorporated in mesoporous MCM‐41 materials by (i) hydrothermal synthesis in the presence of hexadecyltrimethylammonium chloride as surfactant and (ii) impregnation of pre‐synthesized calcined Si‐MCM‐41. The ordering of the hexagonal MCM‐41 structures is revealed from X‐ray diffractograms and nitrogen adsorption isotherms. The dispersion and the coordination of the Ti in the walls or in the pores is deduced from UV/Vis diffuse reflectance spectra (DR‐UV/Vis). The amount of Ti built into the walls of the MCM‐41 under maintenance of a perfect hexagonal structure is restricted to about 2 wt.‐%. In the pores up to 8 wt.‐% Ti can be fixed a silanol groups under molecular, i.e. non‐aggregated, dispersion. The degree of dispersion of ZnPc is concluded from the analysis of the Q‐band structure in the DR‐UV/Vis spectra. Predominantly non‐aggregated ZnPcs in a monomeric state can be obtained, (i) if the ZnPC is incorporated in the micellar structure of the surfactant molecules by adding it to the synthesis gel of the MCM‐41 or (ii) if the ZnPc is adsorbed to Ti‐MCM‐41 with Ti species in high dispersion in the pores. A tight contact between the donor ZnPc and the acceptor titanium oxide, enables an electron transfer and a quenching of the fluorescence of the dye.