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Microwave Spectroscopy of Large Molecules and Molecular Complexes

  1. Walther Caminati

Published Online: 15 SEP 2011

DOI: 10.1002/9780470749593.hrs035

Handbook of High-resolution Spectroscopy

Handbook of High-resolution Spectroscopy

How to Cite

Caminati, W. 2011. Microwave Spectroscopy of Large Molecules and Molecular Complexes. Handbook of High-resolution Spectroscopy. .

Author Information

  1. “G. Ciamician” dell'Università di Bologna, Dipartimento di Chimica, Bologna, Italy

Publication History

  1. Published Online: 15 SEP 2011


The development of Fourier transform microwave (FTMW) spectroscopy and — most notably — its combination with supersonic-jet expansion techniques allow for challenging investigations of larger and larger interesting molecular systems.

Large isolated molecules studied by microwave (MW) spectroscopy include long carbon chains of astronomical interest, organic molecules containing two or more aromatic rings, small biomolecules, and transition metal complexes. Often, these systems are characterized by large-amplitude motions and multifolded conformational and tautomeric equilibria.

Rotational spectra have been reported for many large molecular complexes, such as adducts of large organic and biological molecules with rare gases, water (or other small proton donors/acceptors), and oligomers and hetero adducts of large molecules. Some of these complexes have interaction energies that are in the intermediate regime between bonding and nonbonding (charge-transfer complexes), and some of them, involving chiral molecules, act as a guide to understanding molecular recognition. In addition, the rotational spectra of several carbonyl sulfide (OCS)[BOND]Hen species have been measured (up to n = 39), providing useful data to model superfluidity.

The potentiality of MW spectroscopy to obtain spectroscopic and chemical information on these systems is demonstrated by numerous investigations. Many interesting examples, most of them achieved in the last two decades, have been compiled here.


  • Fourier transform spectroscopy;
  • supersonic expansions;
  • long-chain molecules;
  • astrophysical molecules;
  • fused-ring molecules;
  • transition metal complexes;
  • biomolecules;
  • molecular complexes;
  • van der Waals complexes;
  • molecular aggregation;
  • molecular solvation;
  • quantum solvation;
  • oligomers;
  • hydrogen bonding;
  • noncovalent interaction;
  • charge transfer;
  • molecular recognition