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Carolyn Brock

Research Interests:
Systematics of packing in molecular crystals
Space-group frequencies
Pseudosymmetric and high-Z' structures
Sequences of phase transitions

Ph.D., Northwestern University, 1972
B.A., Wellesley College, 1968


Professor Brock's research interests center on the structures and properties of molecular crystals. She is particularly interested in the systematics of packing in molecular crystals, and in the design, synthesis, and characterization of solid-state molecular complexes.

Systematics of Crystal Packing

Two types of questions are being investigated. First, to what extent does molecular recognition break down during crystal growth? How often are impurities incorporated into growing crystals? How often are solid solutions formed? We are studying this question by characterizing the crystals precipitated from solutions containing two similar solutes, e.g., two different para-substituted benzoic acids or two different members of the series C6(CH3)nCl6-n. The crystals may be formed exclusively of one solute or the other, the crystals may be solid solutions, or a solid-state compound may be formed. Second, we are using the Cambridge Structural Database to answer more general questions about crystal packing; e.g., how often is the symmetry of a molecule maintained in its crystals? If a molecule has a six-fold rotation axis in solution, what is the chance that its crystals are hexagonal?

Phase Relationships: Polymorphs and Solid-State Molecular Complexes

We are combining information from single-crystal and powder diffraction studies with the results of thermal measurements to construct schematic phase diagrams for molecular crystals. While studying trans-1,2-cyclohexanediol (CHD) in this way we discovered an unusual layered compound of the diol with triphenylphosphine oxide (TPPO).

Graduate Training

Physical Chemistry

Professional Responsibilities
Selected Publications:
  • C. P. Brock, “Prevalence and Significance of Approximate Symmetry in Organic Pc Structures”, Helv. Chimica Acta2023106, e202200170.
  • C. P. Brock, “Pervasive Approximate Periodic Symmetry in Organic P1 Structures”, Acta Cryst.2022B78, 576–588.
  • C. P. Brock and R. Taylor, “Identifying and Characterizing Translationally Modulated Molecular Crystal Structures”, Acta Cryst., 2020, B76, 630–642.
  • C. P. Brock, “Pseudosymmetric Layers in High-Z’ and P1 Structures of Organic Molecules”, CrystEngComm 2020, 22, 7371–7379.
  • C.P. Brock, “High-Z’ Structures of Organic Molecules:  Their Diversity and Organizing Principles", Acta Cryst., 2016B72, 807-821.
  • E. Wachter, E. C. Glazer, S. Parkin & C.P. Brock, “An Exceptional 5:4 Enantiomeric Structure”, Acta Cryst., 2016, B72, 223-231.
  • R. C. Bakus II, D. A. Atwood, S. Parkin, C. P. Brock & V. Petříček, “C6H4S2AsCl:  Description and Interpretation of an Incommensurately Modulated Molecular Crystal Structure”, Acta Cryst., 2013, 496-508.
  • M. A. Siegler, S. Parkin & C. P. Brock, “[Ni(MeCN)(H2O)2(NO3)2] (15-crown-5) MeCN:  Detailed Study of a Four-Phase Sequence that Includes an Intermediate Modulated Phase”, Acta Cryst., 2012, B68, 389-400.
  • C. P. Brock, “Learning from Outliers”, ACA Transactions, 2012, 43, 45-64.  pdf
  • M. A. Siegler, X. Hao, S. Parkin & C. P. Brock, "[Ni(H2O)6](NO3)2·(15-crown-5)·2H2O:  Three Phase Transitions and an Intermediate Modulated Phase Stable over a range of ca. 40 K”,Acta Cryst., 2011, B67, 486-498.
  • M. A. Siegler, S. Parkin, R. J. Angel & C. P. Brock, "Detailed Study of the Phase Transition in [Ni(H2O)6](NO3)2.(15-crown-5)].H2O and Analysis in Terms of Mean-Field Theory", Acta Cryst., 2011, B67, 130-143.
  • S. P. Kelley, L. Fábián & C. P. Brock, "Failures of Fractional Crystallization: Ordered Co-Crystals of Isomers and Near Isomers", Acta Cryst., 2011, B67, 79-93.
  • M. A. Siegler, J. H. Prewitt, S. P. Kelley, S. Parkin, J. P. Selegue & C. P. Brock, "More examples of the 15-crown-5···H2O-M-OH2···15-crown-5 motif, M = Al3+, Cr3+ and Pd2+", Acta Cryst., 2010, B66, 213-221.
  • L. Fábián & C. P. Brock, "A List of Organic Kryptoracemates", Acta Cryst., 2010, B66, 94-103.
  • M. A. Siegler, Z. Hao, S. Parkin & C. P. Brock, "Five More Phases of the Structural Family [M(H2O)2(15-crown-5)](NO3)2", Acta Cryst., 2008, B64, 738-749.
  • M. A. Siegler, S. Parkin, J. P. Selegue & C. P. Brock, "The Elusive [Ni(H2O)2 (15-crown-5)]2+ Cation and Related Co-Crystals of Ni(II) Hydrates and 15-Crown-5", Acta Cryst., 2008, B64, 725-737.
  • S. Long, S. Parkin, M. Siegler, C. P. Brock, A. Cammers & T.Li, "Polymorphism of an Organic System Effected by the Directionality of Hydrogen-Bonding Chains", Cryst. Growth Des., 2008, 8, 3137-3140.
  • M. A. Siegler, Y. Fu, G. H. Simpson, D. P. King, S. Parkin & C. P. Brock, "An Unexpected Co-Crystal with a Variable Degree of Order: 1:1 rac-1,2-Cyclohexanediol/Triphenylphosphine Oxide", Acta Cryst., 2007, B63, 912-925.
  • M. A. Lloyd, G. E. Patterson, G. H. Simpson, L. L. Duncan, D. P. King, Y. Fu, B. O. Patrick, S. Parkin & C. P. Brock, "Solid-State Compounds of Stereoisomers: cis and trans Isomers of 1,2-Cyclohexanediol and 2,3-Tetralindiol", Acta Cryst., 2007, B63, 433-447.
  • B. O. Patrick & C. P. Brock, "S,S-1,2-Dicyclohexylethane-1,2-diol and Its Racemic Compound: A Striking Exception to Wallach's Rule", Acta Cryst., 2006, B62, 488-497.
  • X. Hao, S. Parkin & C. P. Brock, "The Unusual Phases of Anhydrous and Hydrated Pinacol", Acta Cryst., 2005, B61, 689-699.
  • X. Hao, M. A. Siegler, S. Parkin & C. P. Brock, "[M(H2O)2(15-crown-5)](NO3)2: A System Rich in Polymorphs and Modulated Phases", Cryst. Growth Des., 2005, 5, 2225-2232.
  • X. Hao, S. Parkin & C. P. Brock, "Three Modulation Patterns in Four Related [M(15-crown-5)(H2O)2](NO3)2 Structures", ", Acta Cryst., 2005, B61, 675-688.
  • X. Hao, J. Chen, A. Cammers, S. Parkin & C. P. Brock, "A Helical Structure with Z'=10", Acta Cryst., 2005, B61, 218-226.
  • H.-J. Lehmler, S. Parkin & C. P. Brock, "Packing Conflicts in the Z'=5 Structure of CF3(CF2)3(CH2)10COOH", Acta Cryst., 2004, B60, 325-332.
  • C. P. Brock, " Crystal Packing in Vicinal Diols CnHm(OH)2", Acta Cryst., 2002, B58, 1025–1031.C. P. Brock, " Crystal Packing in Vicinal Diols CnHm(OH)2", Acta Cryst., 2002, B58, 1025–1031.
  • P. A. Koutentis, R. C. Haddon, R. T. Oakley, A. W Cordes & C. P. Brock, "Perchlorophenalenyl Radical, C13Cl9:  A Modulated Structure with Nine Threefold-Symmetric Molecules in the Asymmetric Unit", Acta Cryst., 2001, B57, 680–691.
  • M. A. Lloyd & C. P. Brock,  "Retention of 4-bar Symmetry in Compounds Containing MAr4 Molecules and Ions", Acta Cryst1997, B53, 780–786.
  • C. P. Brock & L. L. Duncan, "Anomalous Space-Group Frequencies for Monoalcohols CnHmOH", Chem. Mater. 1994, 6, 1307–1312.
  • C. P. Brock & J. D. Dunitz, "Towards a Grammar of Crystal Packing", Chem. Mater. 1994, 6, 1118–1127.
  • C. P. Brock, W. B. Schweizer & J. D. Dunitz, "On the Validity of Wallach's Rule:  On the Density and Stability of Racemic Crystals Compared with Their Chiral Counterparts", J. Am. Chem. Soc. 1991, 113, 9811–9820.
  • C. P. Brock & R. P. Minton, "Systematic Effects of Crystal-Packing Forces:  Biphenyl Fragments with H Atoms in All Four Ortho Positions", J. Am. Chem. Soc. 1989, 111, 4586–4593.