  As the inventory of interstellar molecules continues to grow, the gulf
between small species, whose individual rotational lines can be observed with
radio telescopes, and large ones, such as polycyclic aromatic hydrocarbons
(PAHs) best studied in bulk via infrared and optical observations, is slowly
being bridged. Understanding the connection between these two molecular
reservoirs is critical to understanding the interstellar carbon cycle, but will
require pushing the boundaries of how far we can probe molecular complexity
while still retaining observational specificity. Toward this end, we present a
method for detecting and characterizing new molecular species in single-dish
observations toward sources with sparse line spectra. We have applied this
method to data from the ongoing GOTHAM (GBT Observations of TMC-1: Hunting
Aromatic Molecules) Green Bank Telescope (GBT) large program, discovering six
new interstellar species. In this paper we highlight the detection of
HC$_{11}$N, the largest cyanopolyyne in the interstellar medium.
