Qualitative MO theory of some ring and ladder polymers

1986 ◽  
Vol 90 (25) ◽  
pp. 6602-6610 ◽  
Author(s):  
John P. Lowe ◽  
Sherif A. Kafafi ◽  
John P. LaFemina
Keyword(s):  
Ladder Polymers ◽  
Mo Theory

Resolving the Quadruple Bonding Conundrum in C2 Using Insights Derived from Excited State Potential Energy Surfaces: A Molecular Orbital Perspective

2019 ◽  
Author(s):  
Ishita Bhattacharjee ◽  
Debashree Ghosh ◽  
Ankan Paul
Keyword(s):  
Excited State ◽  
Potential Energy ◽  
Molecular Orbital ◽  
High Spin ◽  
Potential Energy Surfaces ◽  
Valence Bond ◽  
Deep Minimum ◽  
State Potential ◽  
Energy Surfaces ◽  
Mo Theory

The question of quadruple bonding in C<sub>2</sub> has emerged as a hot button issue, with opinions sharply divided between the practitioners of Valence Bond (VB) and Molecular Orbital (MO) theory. Here, we have systematically studied the Potential Energy Curves (PECs) of low lying high spin sigma states of C<sub>2</sub>, N<sub>2</sub> and Be<sub>2</sub> and HC≡CH using several MO based techniques such as CASSCF, RASSCF and MRCI. The analyses of the PECs for the<sup> 2S+1</sup>Σ<sub>g/u</sub> (with 2S+1=1,3,5,7,9) states of C<sub>2</sub> and comparisons with those of relevant dimers and the respective wavefunctions were conducted. We contend that unlike in the case of N<sub>2</sub> and HC≡CH, the presence of a deep minimum in the <sup>7</sup>Σ state of C<sub>2</sub> and CN<sup>+</sup> suggest a latent quadruple bonding nature in these two dimers. Hence, we have struck a reconciliatory note between the MO and VB approaches. The evidence provided by us can be experimentally verified, thus providing the window so that the narrative can move beyond theoretical conjectures.

How rigid are conjugated non‐ladder and ladder polymers?

2021 ◽  
Author(s):  
Zhiqiang Cao ◽  
Mingwan Leng ◽  
Yirui Cao ◽  
Xiaodan Gu ◽  
Lei Fang
Keyword(s):  
Ladder Polymers

Role of population analysis in LCAO-MO theory of transition-metal clusters

1975 ◽  
Vol 25 (11) ◽  
pp. 1201-1207 ◽  
Author(s):  
J. Málek ◽  
R. A. Evarestov ◽  
A. N. Ermoshkin ◽  
B. Hejda ◽  
K. Polák
Keyword(s):  
Transition Metal ◽  
Metal Clusters ◽  
Population Analysis ◽  
Transition Metal Clusters ◽  
Lcao Mo Theory ◽  
Lcao Mo ◽  
Mo Theory

Spectroscopic and morphological studies of highly conducting ion-implanted rigid-rod and ladder polymers

1992 ◽  
Vol 25 (21) ◽  
pp. 5828-5835 ◽  
Author(s):  
John A. Osaheni ◽  
Samson A. Jenekhe ◽  
Andrew Burns ◽  
Gang Du ◽  
Jinsoo Joo ◽  
...  
Keyword(s):  
Morphological Studies ◽  
Ladder Polymers ◽  
Rigid Rod ◽  
Ion Implanted

Nonlinear optical properties of benzimidazobenzophenanthroline type ladder polymers

1990 ◽  
Vol 56 (8) ◽  
pp. 712-714 ◽  
Author(s):  
J. R. Lindle ◽  
F. J. Bartoli ◽  
C. A. Hoffman ◽  
O.‐K. Kim ◽  
Y. S. Lee ◽  
...  
Keyword(s):  
Optical Properties ◽  
Nonlinear Optical ◽  
Nonlinear Optical Properties ◽  
Ladder Polymers

scholarly journals The ‘Inverted Bond’ revisited. Analysis of ‘in silico’ models and of [1.1.1]Propellane using Orbital Forces

2019 ◽  
Author(s):  
Rubén Laplaza ◽  
Julia Contreras-García ◽  
Franck Fuster ◽  
François Volatron ◽  
Patrick Chaquin
Keyword(s):  
Total Energy ◽  
Molecular Orbital ◽  
In Silico ◽  
Bond Energies ◽  
Parent Molecule ◽  
Ca 50 ◽  
In Silico Models ◽  
Mo Theory

<div>This article dwells on the nature of “inverted bonds”, which make reference to the σ interaction between two s-p hybrids by their smaller lobes, and their presence in [1.1.1]propellane <b>1</b>. Firstly we study H 3 C-C models of C-C bonds with frozen HCC angles reproducing the constraints of various degrees of “inversion”. Secondly, the molecular orbital (MO) properties of [1.1.1]propellane <b>1</b> and [1.1.1]bicyclopentane <b>2</b> are analyzed with the help of orbital forces as a criterion of bonding/antibonding character and as a basis to evaluate bond energies. Triplet and cationic state of <b>1</b> species are also considered to confirm the bonding/antibonding character of MOs in the parent molecule. These approaches show an essentially non-bonding character of the σ central CC interaction in propellane. Within MO theory, this bonding is thus only due to π-type MOs (also called ‘banana’ MOs or ‘bridge’ MOs) and its total energy is evaluated to ca. 50 kcal/mol. In bicyclopentane <b>2</b>, despite a strong σ-type repulsion, a weak bonding (15-20 kcal/mol) exists between both central CC, also due to π-type interactions, though no bond is present in the Lewis structure. Overall, the so-called ‘inverted’ bond, as resulting from a σ overlap of the two s-p hybrids by their smaller lobes, appears highly questionable.</div>

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