The interaction of the diatomic molecules, H-2, N-2, O-2, CO, and NO, with the anions, H-, Li-, and F- is theoretically examined using a density functional method (B3LYP). It was found that the charge transfer from the anions to diatomic molecules easily occurs and overcomes the electronic repulsion to form the anion clusters. The clustering of the H-2 around H-is controlled by the novel conjugation through the sigma* orbitals of the H-2 coordinated to the H- anion center. For the other diatomic molecules, the pi* orbital plays a key role on the clustering process. The charge transfer from the H- or Li-to the pi* orbital of the N-2, O-2, CO, and NO induces the attractive interaction between the pi* orbitals and generates the anion cluster with a pentagonal cyclic form consisting of two diatomic molecules and one anion, which is unknown so far according to our knowledge. The geometric structure of the anion cluster significantly depends on the electronic nature of the anions and the diatomic molecules. The interaction in the clustering as well as the geometric structure is discussed in detail.