Subtopic Deep Dive
Hydrogen Bonding in Molecular Crystals
Research Guide
What is Hydrogen Bonding in Molecular Crystals?
Hydrogen bonding in molecular crystals refers to the directional intermolecular interactions where a hydrogen atom covalently bonded to an electronegative atom forms a bond with another electronegative atom, dictating crystal packing and stability.
These bonds are analyzed using crystallographic data from X-ray diffraction and computational tools like Hirshfeld surfaces. Key methods include PLATON validation (Spek, 2003; 13729 citations) and energy frameworks in CrystalExplorer (Mackenzie et al., 2017; 1268 citations). Over 10 high-citation papers from 1994-2020 highlight geometry, strength, and cooperativity in organic solids.
Why It Matters
Hydrogen bonds control supramolecular synthons in pharmaceutical crystals, enabling prediction of polymorphs for drug stability (Gilli and Gilli, 2009). In materials science, they govern packing motifs in organic solids, influencing properties like solubility and conductivity (Spackman and McKinnon, 2002). Energy frameworks from CrystalExplorer quantify interaction strengths, aiding crystal engineering designs (Mackenzie et al., 2017).
Key Research Challenges
Accurate Structure Validation
Disordered solvents complicate refinement, requiring tools like PLATON SQUEEZE to model contributions (Spek, 2014; 3620 citations). Validation alerts detect errors in CIF files from exponential growth in analyses (Spek, 2009; 15141 citations). This ensures reliable hydrogen bond geometries.
Quantifying Weak Interactions
Hirshfeld surfaces fingerprint hydrogen and van der Waals contacts but need calibration for energy frameworks (Spackman and McKinnon, 2002; 3828 citations). Distinguishing CH/π from traditional O-H···O bonds challenges cooperativity assessment (Nishio, 2004; 1401 citations).
Modeling Cooperative Effects
Quantum chemical calculations struggle with large crystals, relying on extended tight-binding methods for scalability (Bannwarth et al., 2020; 1400 citations). Charge density distributions reveal bond strengths but demand high-resolution data (Álvarez, 2013; 1482 citations).
Essential Papers
Structure validation in chemical crystallography
Anthony L. Spek · 2009 · Acta Crystallographica Section D Biological Crystallography · 15.1K citations
Automated structure validation was introduced in chemical crystallography about 12 years ago as a tool to assist practitioners with the exponential growth in crystal structure analyses. Validation ...
Single-crystal structure validation with the program<i>PLATON</i>
Anthony L. Spek · 2003 · Journal of Applied Crystallography · 13.7K citations
The results of a single-crystal structure determination when in CIF format can now be validated routinely by automatic procedures. In this way, many errors in published papers can be avoided. The v...
Fingerprinting intermolecular interactions in molecular crystals
Mark A. Spackman, Joshua J. McKinnon · 2002 · CrystEngComm · 3.8K citations
We have recently described a remarkable new way of exploring packing modes and intermolecular interactions in molecular crystals using a novel partitioning of crystal space. These molecular Hirshfe...
<i>PLATON</i>SQUEEZE: a tool for the calculation of the disordered solvent contribution to the calculated structure factors
Anthony L. Spek · 2014 · Acta Crystallographica Section C Structural Chemistry · 3.6K citations
The completion of a crystal structure determination is often hampered by the presence of embedded solvent molecules or ions that are seriously disordered. Their contribution to the calculated struc...
A cartography of the van der Waals territories
Santiago Álvarez · 2013 · Dalton Transactions · 1.5K citations
The distribution of distances from atoms of a particular element E to a probe atom X (oxygen in most cases), both bonded and intermolecular non-bonded contacts, has been analyzed. In general, the d...
CH/? hydrogen bonds in crystals
Motohiro Nishio · 2004 · CrystEngComm · 1.4K citations
The nature and characteristics of the CH/π interaction are discussed by comparison with other weak molecular forces such as the CH/O and OH/π interaction. The CH/π interaction is a kind of hydrogen...
Extended <scp>tight‐binding</scp> quantum chemistry methods
Christoph Bannwarth, Eike Caldeweyher, Sebastian Ehlert et al. · 2020 · Wiley Interdisciplinary Reviews Computational Molecular Science · 1.4K citations
Abstract This review covers a family of atomistic, mostly quantum chemistry (QC) based semiempirical methods for the fast and reasonably accurate description of large molecules in gas and condensed...
Reading Guide
Foundational Papers
Start with Spek (2009; 15141 citations) for validation essentials, then Spackman and McKinnon (2002; 3828 citations) for Hirshfeld surfaces to understand interaction mapping.
Recent Advances
Study Mackenzie et al. (2017; 1268 citations) for energy frameworks in coordination compounds and Bannwarth et al. (2020; 1400 citations) for scalable quantum modeling.
Core Methods
Core techniques: PLATON/checkCIF validation (Spek, 2003), Hirshfeld surfaces (Spackman and McKinnon, 2002), CrystalExplorer energies (Mackenzie et al., 2017), and tight-binding QC (Bannwarth et al., 2020).
How PapersFlow Helps You Research Hydrogen Bonding in Molecular Crystals
Discover & Search
Research Agent uses searchPapers and citationGraph to map Spek (2009; 15141 citations) as the foundational validation hub, revealing 50+ connected papers on hydrogen bond geometry. exaSearch uncovers niche CH/π interactions from Nishio (2004), while findSimilarPapers extends to energy frameworks like Mackenzie et al. (2017).
Analyze & Verify
Analysis Agent applies readPaperContent to extract Hirshfeld surface data from Spackman and McKinnon (2002), then verifyResponse with CoVe checks computational claims against crystallographic evidence. runPythonAnalysis computes bond distances via NumPy on CIF data, with GRADE scoring evidence strength for cooperativity claims.
Synthesize & Write
Synthesis Agent detects gaps in polymorph prediction from hydrogen bond motifs, flagging contradictions between PLATON alerts (Spek, 2003) and energy models. Writing Agent uses latexEditText for crystal diagrams, latexSyncCitations for 20+ references, and latexCompile to generate IUCrJ-style reports; exportMermaid visualizes interaction networks.
Use Cases
"Analyze hydrogen bond distances in this CIF file for cooperativity."
Analysis Agent → readPaperContent (CIF upload) → runPythonAnalysis (NumPy distance matrix + matplotlib plot) → statistical verification of D···A < 3.5 Å thresholds.
"Write a review on Hirshfeld surfaces in molecular crystals with diagrams."
Synthesis Agent → gap detection → Writing Agent → latexEditText (section drafting) → latexGenerateFigure (surface plots) → latexCompile (PDF output with synced citations).
"Find GitHub code for CrystalExplorer energy frameworks."
Research Agent → paperExtractUrls (Mackenzie et al., 2017) → Code Discovery → paperFindGithubRepo → githubRepoInspect → verified Python scripts for interaction energies.
Automated Workflows
Deep Research workflow scans 50+ papers from Spek (2009) citation graph, generating structured reports on validation for hydrogen bonds. DeepScan's 7-step chain verifies disordered solvent models (Spek, 2014) with CoVe checkpoints and Python analysis. Theorizer hypothesizes new synthons from Hirshfeld data (Spackman and McKinnon, 2002).
Frequently Asked Questions
What defines hydrogen bonding in molecular crystals?
It involves a hydrogen attached to N, O, or F interacting directionally with another electronegative atom, analyzed via X-ray geometry and energies (Gilli and Gilli, 2009).
What are key methods for analysis?
PLATON for validation (Spek, 2003), Hirshfeld surfaces for fingerprinting (Spackman and McKinnon, 2002), and CrystalExplorer for energy frameworks (Mackenzie et al., 2017).
What are seminal papers?
Spek (2009; 15141 citations) on validation, Spackman and McKinnon (2002; 3828 citations) on surfaces, Nishio (2004; 1401 citations) on CH/π bonds.
What open problems exist?
Quantifying cooperative effects in large crystals and distinguishing weak CH/π from strong bonds; scalable QC methods like tight-binding help (Bannwarth et al., 2020).
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