Formaldehyde, excited state geometry

Figure 4.19 Ground slate and excited state geometry of formaldehyde molecule.

Another example of the idea of congruency of transition state and excited state geometry can be found in the chemiluminescent reaction of 1,2-dioxetanes (6). The excited state of formaldehyde is known to be bent, with the... 

Excitation and geometry. Although the initially formed electronically excited state of formaldehyde, HaC=0, has the same shape as the ground sfrite, it quickly relaxes to a pyramidal structure, (a) Draw a reasonable electronic structure for pyramidal H C and compare it with the planar excited form. 

Figure 5.11. Geometry of formaldehyde in its (a) ground, (b) first excited singlet, and (c) first excited triplet electronic states.

As can be easily visualized from Figure 4.19, formaldehyde molecule has a planar geometry in the ground state. On excitation to the n, n) state, an electron localized on O-atom is transferred to an anti-bonding n-MO which has a node between C and O bonds. This destroys the... 

Figure 1.9 Geometry of tai the lowest tit.tt ) excited singlet state ol ethylene, ib) the lowest tJi.n ) excited singlet state of acetylene, and (c) the lowest in. n l state of formaldehyde...

Figure 18-9 Geometry of formaldehyde (a) Ground state, (b) Lowest excited singlet state.

Thus far, attention has been focused on the guest molecules in their ground states. This is so because it is relatively easy to predict and visualize the geometry and orientation of molecules within reaction cavities based on attractive and repulsive interactions between ground state guest molecules and the host structure. However, electronic excitation frequently lead to changes in molecular geometry and polarizability [97], For example, it is well known that formaldehyde becomes pyramidal upon excitation and the C—O... 

Figure 2 4. The calculated excitation energies to some low-lying states of formaldehyde. The basis set, geometry, and other details are found in Refs. [60, 61, 67, 69]...

Valence excitation energies for formaldehyde [36]. The second example is the GMC-QDPT calculation of valence excitation energies for formaldehyde molecule. Calculations on formaldehyde were carried out at the ground state experimental geometry (i.e. r(CO) = 1.203 A, r(CH) = 1.099 A, and 0(HCH) = 116.5°). The basis set used was Dunning s cc-pVTZ. 

Figure 19-17 Geometry of formaldehyde in its ground state (So) and lowest excited singlet state (Si).

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