A molecular-wire crossbar interconnect for signal routing and communications between a first level and a second level in a molecular-wire crossbar is provided. The molecular wire crossbar comprises a two-dimensional array of a plurality of nanometer-scale switches. Each switch is reconfigurable and self-assembling and comprises a pair of crossed wires which form a junction where one wire crosses another and at least one connector species connecting the pair of crossed wires in the junction. The connector species comprises a bi-stable molecule. Each level comprises at least one group of switches and each group of switches comprises at least one switch, with each group in the first level connected to all other groups in the second level in an all-to-all configuration to provide a scalable, defect-tolerant, fat-tree networking scheme. The primary advantage is ease of fabrication, because an active switch is formed any time two wires cross. This saves tremendously on circuit area (a factor of a few times ten), since no other wires or ancillary devices are needed to operate the switch or store the required configuration. This reduction of the area of a configuration bit and its switch to just the area of two crossing wires is a major advantage in constructing a defect-tolerant interconnect network.