In recent years, it has become possible to synthesize gold clusters, silver clusters, and alloy clusters with atomic precision using thiolate or phosphine (PR3) as a ligand. The electronic/geometric structures and size-specific physical/chemical properties of these metal clusters have also been investigated extensively. Similar to these metal clusters, platinum (Pt) clusters have also attracted much interest. An attractive feature of Pt clusters is their high catalytic activity in a variety of reactions. In the precise synthesis of these Pt clusters, carbon monoxide (CO) or PR3 is used as the main ligand. However, little information has been obtained on the electronic structure and physical/chemical properties of Ptn(CO)m(PR3)l clusters to date. In this research, the final objective is to obtain experimental information about the largely unknown electronic structure of Ptn(CO)m(PR3)l clusters. To this end, we precisely synthesized a Pt17 cluster ([Pt17(CO)12(PPh3)8]n+; n = 1, 2) protected by CO and triphenylphosphine (PPh3) by a simple method and studied its geometric and electronic structure. Mass spectrometry, elemental analysis, and single-crystal X-ray structural analysis of the product revealed that the obtained Pt17(CO)12(PPh3)8 comprises positively charged [Pt17(CO)12(PPh3)8]+ and [Pt17(CO)12(PPh3)8]2+, having a geometric structure similar to that36 of neutral Pt17(CO)12(PEt3)8. The optical absorption spectroscopy and electrochemical measurements of [Pt17(CO)12(PPh3)8][(SbF6)n] (n = 1, 2) demonstrated that [Pt17(CO)12(PPh3)8][(SbF6)n] (n = 1, 2) has a discrete electronic structure. Furthermore, the emission spectroscopy revealed that [Pt17(CO)12(PPh3)8][(SbF6)n] (n = 1, 2) exhibits photoluminescence in the near-infrared region. In this presentation, I also talk about our recent results on the precise synthesis and one-dimensional structures of alloy clusters including Pt element.