SECTION 1: TUTORIAL Frameworks for Extended Solids: Geometrical Design Principles

In this tutorial article we present the basic topologies (nets) that underlie most low-density (&&open'') structures. For illustration we give some examples, often from our own work, of clusters and linkages that are assembled into frameworks, but the main emphasis is on the topologies that can be expected to form and which might reasonably be the target of a designed synthesis. It is our thesis that a few (about a dozen) simple high-symmetry topologies are of paramount importance, and we describe these.1 It is our objective to outline the important connections existing between simple nets and extended structures that are assembled from molecular building blocks.