From owner-chemistry@ccl.net Sun Sep 7 10:41:00 2008 From: "David Eisenberg david.eisen(0)gmail.com" To: CCL Subject: CCL: Ligand substitution calculation Message-Id: <-37721-080907095013-24545-LiNnJljaR6JbBZf5SHWukg^server.ccl.net> X-Original-From: "David Eisenberg" Date: Sun, 7 Sep 2008 09:50:09 -0400 Sent to CCL by: "David Eisenberg" [david.eisen]![gmail.com] Dear CCL users, I've got a really basic and silly question, and would appreciate any help. I want to compare the relative stabilities of two transition-metal complexes: one with ligands that include two chlorides (-Cl), and the other with two hydrides (-H) instead of the chlorides. But to get the Delta-G for the ligand-substitution reaction, the reaction must be balanced. What is the most correct way of balancing it? With molecular Cl2 and H2, or with ions of Cl- and H-, or maybe with Cl* and H* radicals?! Thank you in advance for any help, D. Eisenberg From owner-chemistry@ccl.net Sun Sep 7 12:37:01 2008 From: "Anatoli Korkin a_korkin(_)yahoo.com" To: CCL Subject: CCL: Ligand substitution calculation Message-Id: <-37722-080907123551-17928-Bl9ALGYG3m+t8Zz/bUm/ng++server.ccl.net> X-Original-From: Anatoli Korkin Content-Type: text/plain; charset=us-ascii Date: Sun, 7 Sep 2008 09:35:40 -0700 (PDT) MIME-Version: 1.0 Sent to CCL by: Anatoli Korkin [a_korkin[*]yahoo.com] Stability is always a relative term. For example Si-F bond is one of the strongest bonds in gas phase or non-polar solvents, while F- ions are used to catalyze reactions including breaking and formation of Si-O bonds in polar solvents (nice way to build various porous materials). HCl is a nice stable molecule in gas phase but it does not exist in water. Assume that you have means (computer, program and skills) to calculates accurately total energies of molecules, and calculate or estimate (measure) solvatation energy of your complexes (f they are stable in that particular solvent as molecular complexes). In this case the energy of reaction: XnMCl2 + MHm => XnMH2 + MClm (need to balance stochiometry) will give you are relative heat of formation of your complex XnMH2 compared to XnMCl2, if heats of formations of MHm and MClm are known. If they are not, you can use another reaction but you will need much more accurate QM method to use due to the non-additive correlation effects (read about it in one of the fundamental book on quantum chemistry): XnMCl2 + H2 (or 2HCl) = XxMH2 + Cl2 (or 2Cl2) Heats of formation of H2 and Cl2 are zero and the one of HCl -s -22 kca/mol: http://webbook.nist.gov/cgi/cbook.cgi?ID=C7647010&Units=CAL&Mask=1 Once you know the relative stability of your complexes in gas phase and have the means to calculate (measure, estimate from some additive parameters) solvation energies of your complexes in the solvent you use, then you can estimate relative stability of your complexes in THAT solvent. Complication may arise if your solvent molecules form first coordination ligand bonds with the metal or can replace some of the ligands in your complexes, in this case you have to calculate the full thermodynamic balance of possible species in your system. Good luck :) --- On Sun, 9/7/08, David Eisenberg david.eisen(0)gmail.com wrote: > From: David Eisenberg david.eisen(0)gmail.com > Subject: CCL: Ligand substitution calculation > To: "Korkin, Anatoli " > Date: Sunday, September 7, 2008, 6:50 AM > Sent to CCL by: "David Eisenberg" > [david.eisen]![gmail.com] > Dear CCL users, > > I've got a really basic and silly question, and would > appreciate any help. > > I want to compare the relative stabilities of two > transition-metal > complexes: one with ligands that include two chlorides > (-Cl), and the other > with two hydrides (-H) instead of the chlorides. > > But to get the Delta-G for the ligand-substitution > reaction, the reaction > must be balanced. What is the most correct way of balancing > it? With > molecular Cl2 and H2, or with ions of Cl- and H-, or maybe > with Cl* and H* > radicals?! > > Thank you in advance for any help, > D. Eisenberg > > > > -= This is automatically added to each message by the > mailing script =- > To recover the email address of the author of the message, > please change > the strange characters on the top line to the |*| sign. You > can also> Conferences: > http://server.ccl.net/chemistry/announcements/conferences/ > > Search Messages: http://www.ccl.net/htdig (login: ccl, > Password: search) From owner-chemistry@ccl.net Sun Sep 7 16:33:00 2008 From: "Mr Shabbir shabbir[A]nenu.edu.cn" To: CCL Subject: CCL:G: binding energy with other interactions Message-Id: <-37723-080907163207-31342-6Aij6kS3+Y0QsxPWtbNYcg::server.ccl.net> X-Original-From: "Mr Shabbir" Date: Sun, 7 Sep 2008 16:32:03 -0400 Sent to CCL by: "Mr Shabbir" [shabbir : nenu.edu.cn] Hi CCL users I am working on anion detecting sensors. In my project I am interested to see the interaction of a boron containing sensor with different anion eg F,Cl,Br,OH etc. For their comparative study I have calculted the binding energies of sensor and these ions.This binding energy is alone not looking reasoable to explain these interaction .Is there any other property that can also support the trend of calculated binding energies of these complexs using Gaussian,NBO,AOMix etc...? Mr.Shabbir shabbir]*[nenu.edu.cn