Covalent assembly of molecular ladders

[n]-Rung molecular ladders (n = 3-6) have been prepared by reacting discrete, complimentary m-phenylene ethynylene oligomers using imine formation/exchange. The nanostructures, which in the largest case measure approximately 1.6 × 6.2 nm, have been characterized by MALDI mass spectrometry and gel permeation chromatography. Although the ladder structure is a significant component in each case, the formation of higher molecular weight byproducts becomes more pronounced as the length increases. These structures represent an important first step toward the synthesis of larger, more sophisticated two-dimensional molecular grids.