Porphyrins and metalloporphyrins have been investigated extensively due to their important role in natural photosynthesis, strong absorption in visible region, good light-harvesting properties, unique photophysical and electrochemical properties, and the development of simple synthetic routes for various derivatives. [1][2][3] Dendrimers have globular structure with branches of repeating units and wide diversity of the architecture because their size, shape, and functionalities can be tailored. 4,5 Numerous dendrimers have been designed and synthesized for various applications ranging from catalyst to drug delivery. [6][7][8][9][10] Dendrimers 11,12 into which porphyrins were introduced as core, branches, or surface groups have received great attention from the early days of dendrimer chemistry, in view of mimicking the structure of natural hemoproteins or natural photosynthetic systems. Porphyrin dendrimers have features of both desirable photophysical and redox properties of porphyrins and synthetically controllable structure of dendrimers, expecting the diverse applications to artificial photosynthesis, lightharvesting, reversible O 2 binding, photodynamic therapy, and optoelectronics.13,14 Moreover, it has been known that selfaggregation or self-association and fluorescence selfquenching of porphyrin was efficiently suppressed, as porphyrin moiety is encapsulated by dendritic environments in porphyrin dendrimers. 15 In most porphyrin dendrimers, dendritic moieties were substituted at the meso-positions of porphyrin ring. 11,13,16 Although dendrimers of various structure have been developed, a few of hybrid dendrimers with different dendron blocks has been reported. 17,18 It is well known that metalloporphyrins form coordination complexes at their axial position with nitrogen ligand such as pyridine. 19,20 It is expected that construction of highdimensional dendrimers and, especially, hybrid dendrimers with different dendron blocks could be easily prepared by axial coordination of pyridine-cored dendron on metalloporphyrin-cored dendrimer.In this work, we report the preparation of various zinc porphyrin dendrimers by noncovalent assembly and how the dendritic environments affect the axial coordination of pyridinecored dendron on zinc porphyrin-cored dendrimers.Pyridine-cored dendrons Py-PD and Py-AD, containing poly(amidoamine) (PAMAM) dendron (PD) and arylether dendron (AD), respectively, and zinc porphyrin-cored dendrimers, ZnP-AD, ZnP-AD 2 , and ZnP-AD 4 , containing one, two, and four arylether dendrons (AD) at the meso-positions of a porphyrin macrocycle, respectively, were prepared by previously reported procedure 19,21 and shown in Figure 1. Metalloporphyrin is a sort of coordination complex, where four pyrrole ligands in the core of porphyrin ring plane are coordinated on central metal. Another additional ligand could be coordinated at axial position on metalloporphyrin plane. 19,22 Upon the complexation with axial ligand, absorption spectra of metalloporphyrin are usually red-shifted and the ε α /ε β ...