Integrated Molecular Structure Education and Research Center (IMSERC) at Northwestern

One of the foremost priorities in materials discovery (both organic and inorganic) is to determine the crystal structure of a material at the atomic scale. The crystallographic determination of the content of the so-called unit cell of a good quality crystal will provide the necessary information for an accurate description of the bonding environment in the crystal structure. Unit cell is essentially the smallest repetitive three-dimensional atomic/molecular building block in a crystal.

After the crystallographic determination of the content of the unit cell in the atomic scale, structural parameters, such as bond-lengths, bond-angles, cation-anion coordination, site-ordering, etc. can be accurately extracted. Crystallographic determination of the content of the unit cell requires collection of diffraction intensity data which is typically collected with X-rays, electrons, and neutrons. After data collection, a series of data reduction, solution, and refinement steps must occur in order to obtain the content of the unit cell.

The packing and arrangement of molecules within a crystal structure is important for studying the intermolecular interactions between molecules, e.g. Hydrogen bonding, absolute structure, etc. Crystallographic analyses of single crystal diffraction data could provide information on the absolute structure of a good quality crystal. Hence, for example, it is possible to 1) determine the packing of molecules and co-crystals in new compounds, and/or 2) differentiate between enantiomers in inorganic materials, natural products, etc.

Absolute structure determination by single crystal crystallographic techniques can provide information about the structural chirality, absolute chirality, absolute polarity, absolute morphology, absolute chiral morphology, and absolute polar morphology of a compound.

The packing and arrangement of molecules within a crystal structure is important for studying the intermolecular interactions between molecules, e.g. Hydrogen bonding, absolute structure, etc. Crystallographic analyses of single crystal diffraction data could provide information on the absolute structure of a good quality crystal. Hence, for example, it is possible to 1) determine the packing of molecules and co-crystals in new compounds, and/or 2) differentiate between enantiomers in inorganic materials, natural products, etc.

Absolute structure determination by single crystal crystallographic techniques can provide information about the structural chirality, absolute chirality, absolute polarity, absolute morphology, absolute chiral morphology, and absolute polar morphology of a compound.

The packing and arrangement of molecules within a crystal structure is important for studying the intermolecular interactions between molecules, e.g. Hydrogen bonding, absolute structure, etc. Crystallographic analyses of single crystal diffraction data could provide information on the absolute structure of a good quality crystal. Hence, for example, it is possible to 1) determine the packing of molecules and co-crystals in new compounds, and/or 2) differentiate between enantiomers in inorganic materials, natural products, etc.

Absolute structure determination by single crystal crystallographic techniques can provide information about the structural chirality, absolute chirality, absolute polarity, absolute morphology, absolute chiral morphology, and absolute polar morphology of a compound.

A modulated crystal structure, in simple terms, is quasi-periodic, i.e., its periodicity cannot be defined by traditional three-dimensional lattice parameters and requires additional vectors to define its periodicity. Modulation vectors and structure solution of modulated structures can be determined crystallographically. If the components of the modulation vector are all rational numbers, the structure is called commensurately modulated. In case one of the components of the vector is an irrational number, the structure is called incommensurately modulated.

Twinning occurs when a crystal possesses domains in different orientations and can be related by a translation, rotation, inversion, or reflection. Depending on the degree of twinning in a material, either single crystal or powder crystallographic techniques can be utilized for a proper structure elucidation.

One of the foremost priorities in materials discovery (both organic and inorganic) is to determine the crystal structure of a material at the atomic scale. The crystallographic determination of the content of the so-called unit cell of a good quality crystal will provide the necessary information for an accurate description of the bonding environment in the crystal structure. Unit cell is essentially the smallest repetitive three-dimensional atomic/molecular building block in a crystal.

After the crystallographic determination of the content of the unit cell in the atomic scale, structural parameters, such as bond-lengths, bond-angles, cation-anion coordination, site-ordering, etc. can be accurately extracted. Crystallographic determination of the content of the unit cell requires collection of diffraction intensity data which is typically collected with X-rays, electrons, and neutrons. After data collection, a series of data reduction, solution, and refinement steps must occur in order to obtain the content of the unit cell.

In many cases and especially in exploratory research, it is quite challenging to obtain the desired compound/phase with 100% purity. Presence of “unwanted” phase(s), i.e., an impurity, might affect the overall property and proper bulk characterization of a sample. Hence, it is important to “detect and quantify” impurities in a sample. Powder diffraction techniques on bulk samples can provide a detailed compositional map (most of the times down to ~1-2% by weight) of various phases in a sample. Powder crystallography enables quantitative determination of the various crystalline (and sometimes amorphous) components in a mixture.

In many cases and especially in exploratory research, it is quite challenging to obtain the desired compound/phase with 100% purity. Presence of “unwanted” phase(s), i.e., an impurity, might affect the overall property and proper bulk characterization of a sample. Hence, it is important to “detect and quantify” impurities in a sample. Powder diffraction techniques on bulk samples can provide a detailed compositional map (most of the times down to ~1-2% by weight) of various phases in a sample. Powder crystallography enables quantitative determination of the various crystalline (and sometimes amorphous) components in a mixture.

Reactions can be monitored in-situ/operando as a function of time, temperature, pressure, and gas flow by crystallographic diffraction methods. This kind of experiments can provide crucial information regarding metastable or kinetically stable phases during the heating or cooling process that are not generally detected in a tradition reaction setup (reactor, furnace, glassware, etc.) in the laboratory. X-ray or neutron diffraction can be utilized to have direct insight into reactions and crystallization processes and detect any metastable intermediate phase(s).

A catalytic reaction can be probed by in-situ/operando X-ray diffraction methods as a function of time and simultaneously at a specific isothermal or dynamic temperature environment under inert and/or reactive gas flow. The changes in substrate and/or products can be monitored both qualitatively as well as quantitatively that can be used to calculated rate constants or even to determine the nature of chemical kinetics.

Thermal or chemical decomposition mechanism in a material can be monitored in real time using in-situ/operando X-ray diffraction measurements that can be performed as a function of time and/or under non-ambient conditions, such as heating, cooling, oxidizing, reducing, etc.

Additionally, Thermal Analysis coupled with GC-MS and/or IR might yield information regarding the decomposition temperature and identification of generated gas molecules (e.g., water, ammonia, carbon dioxide, etc.) during the decomposition thermal event.

Reactions can be monitored in-situ/operando as a function of time, temperature, pressure, and gas flow by crystallographic diffraction methods. This kind of experiments can provide crucial information regarding metastable or kinetically stable phases during the heating or cooling process that are not generally detected in a tradition reaction setup (reactor, furnace, glassware, etc.) in the laboratory. X-ray or neutron diffraction can be utilized to have direct insight into reactions and crystallization processes and detect any metastable intermediate phase(s).