Crystal Cohesion and Conformational Energies: 26 - Brossura

1. Introduction.- References.- 2. Transferable Empirical Nonbonded Potential Functions.- 2.1 Introductory Comments.- 2.2 Empirical Nonbonded Potential Models.- 2.2.1 The Number of Adjustable Parameters and Heteroatomic Combining Laws.- 2.2.2 The Atomic Hardness Parameters, C.- 2.2.3 The Repulsion Center Shift for Bonded Hydrogen.- 2.2.4 The Net Atomic Charges, q.- 2.3 Nonbonded Interactions in Molecular Crystals.- 2.3.1 Nonbonded Crystal Lattice Energy.- 2.3.2 Mathematical Description of the Crystal Structure.- 2.3.3 The Structural Derivatives of C.- 2.3.4 The Forces and Torques as Functions of the Nonbonded Potential Parameters.- 2.4 Accelerated Convergence of Lattice Sums.- 2.4.1 Fourier Transforms of the Lattice Sum.- 2.4.2 Numerical Examples.- 2.4.3 Lattice Energy Derivatives Including Accelerated Convergence.- 2.5 Derivation of Nonbonded Potential Parameters.- 2.5.1 The Force-Fit Method.- 2.5.2 Application to Hydrocarbons.- 2.5.3 The Direct-Parameter-Fit Method.- 2.6 Extensions of the Potential Model.- 2.6.1 Molecular Rotations and Translations.- 2.6.2 Intramolecular Rotations.- 2.6.3 Thermal Corrections.- 2.6.4 Lattice Vibrations.- 2.6.5 Weak Morse Bond Potential.- 2.6.6 High-Pressure Crystal Structures.- 2.7 Appendix. Derivatives of C.- References.- 3. Conformational Analysis and Polypeptide Drug Design.- 3.1 Introductory Comments.- 3.2 Computational Procedures.- 3.3 Polypeptides and Their Constituents.- 3.3.1 Modifications to the Peptide Backbone.- a) L-Amino Acids.- b) D-Amino Acids.- c) C?-Methyl Analogs.- d) N-Methyl Analogs.- e) Depsipeptides.- f) Reduced Carbonyl. Intercalated Methylene (homo), and Carbazic Acid (?-Aza) Analogs.- 3.3.2 Chain Reversals and Bend Conformations.- a) LL, LD, and DL Bends.- b) Depsipeptide Bend Structures.- 3.3.3 Direction Reversal: Retro, Retroenantiomers, and Retro-all-D-Peptides.- 3.3.4 Bridges: Disulfide Bonds and Carba-Analogs.- 3.3.5 Modifications of Side Chains.- 3.3.6 Abnormal Side-Chain Modifications.- a) ?,?-Dehydro Analogs.- b) 3,4-Dehydroproline, Azetidine, and Thiazolidine.- 3.4 Application of Conformational Information to Drug Design.- 3.4.1 Example Studies: Backbone Substitutions and Conformational Effects.- a) D-Amino Acid Substitution.- Case I: C-terminal of Somatostatin.- Case II: N-terminal of Luteinizing Hormone-Releasing Hormone (LHRH).- Case III: Substitution for Glycine in Enkephalins (EK) and LHRH.- Case IV: L- to D-Conversion in Somatostatin.- Case V: L- to D-Conversions in LHRH Antagonists.- b) N-Methyl and Depsipeptide Results.- Case VI: Eledoisin and [(N-Me)Leu7]-LHRH.- c) L-, D-Combinations.- Case VII: A Conformational Approach to the Design of Growth Hormone Agonist.- 3.5 Conclusions.- References.- 4. Cohesion and Ionicity in Organic Semiconductors and Metals.- 4.1 Introductory Comments.- 4.2 Crystal Cohesive Energies: General Theory.- 4.2.1 Löwdin’s Theory.- 4.2.2 Madelung Energy.- 4.2.3 Charge-Dipole and Dipolar Energies.- 4.2.4 Polarization and Dispersion Energies.- 4.3 Born-Haber Cycles and Criteria for Ionicity.- 4.3.1 Born-Haber Cycles.- 4.3.2 Criteria for Ionicity.- 4.4 Lattice Energy Calculations.- 4.4.1 Lattice Energy Algorithms.- 4.4.2 Madelung Energy-Uniform Lattice.- 4.4.3 Madelung Energy-Wigner Lattice.- 4.4.4 Beyond the Madelung Energy.- References.- 5. Slipped Versus Eclipsed Stacking of Tetrathiafulvalene (TTF) and Tetracyanoquinodimethane (TCNQ) Dimers.- 5.1 Introductory Comments.- 5.2 Geometry of Donor-Acceptor ? Complexes: Slipped Versus Eclipsed Stacking.- 5.3 Molecular-Orbital Calculations.- 5.3.1 Extended-Hückel Calculations.- 5.3.2 CNDO/2 Calculations.- 5.4 Interactions Between Closed-Shell Neutral TTF Molecules: Hard-Sphere Packing and Atom-Atom Potentials in Crystalline TTF.- 5.5 Density-Functional Calculation: Neutral TTF Dimer.- 5.6 Density-Functional Calculation: Open Shell TTF Dimer.- 5.7 Conclusions.- References.

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