H2 CuFAn overview of H2 MX complexes

G.S. Grubbs II, D.J. Frohman, Z. Yu, S.E. Novick

TH13, Columbus 2013Inorg. Chem. 52, 816-822 (2013).

The motivation for these studies is the H2 storagecapacity of Metal Organic Frameworks (MOFs).

Shown if MOF-5 from a review article of Yaghi et. al.

The yellow sphere is unfilled and shows the porosityOf the MOF.

The phenyl rings are shown connecting the Zn4O(CO2)6 units. These units are seen to consist offour ZnO4 tetrahedra (in blue) with a common vertex.The zinc is hidden in the center of the tetrahedra, oxygen atoms are red, carbons are black. MOFs can hold up to 18 weight-percent hydrogen molecules.

We hope to mimic the “active sites” in MOFs in orderto help design MOFs for better H2 storage.

MOF-5

H2 CuF was produced by laser ablation of a copper rod with a gas pulse of 0.6% SF6 and3% H2 in argon with a backing pressure of 5 atm. Standard FTMW spectroscopy wasemployed.

para-H2 63CuF1500 gas pulses

ortho-D2 63CuF2500 gas pulses

natural abundance of 63Cu = 69%; I(63Cu)= 3/2natural abundance of 65Cu = 31%; I(65Cu)= 3/2

Spin statisticsThe total wavefunction for the interchange of the two identical fermions, 1H, is of negative parityThe total wavefunction for the interchange of the two identical bosons, 2H, is of positive parity

The measured a-type transitions all have Ka = 0, and rotational wavefunction is of positive parity

a

The ortho states are symmetric with respectto interchange of the two identical nuclei

rot (1)Ka

Spectroscopic parameters for para-H2 CuF, ortho-D2 CuF, and HD CuF

χaa MHz De kJ/mol α A3 De/α63CuF a 21.9562 -------------- -------------- --------------

Ar CuF a 38.0556 47 1.63 29

Kr CuF b 41.77 45 2.465 18

Xe CuF c 47.76 63 4.01 16

p-H2 CuF 61.275 105 0.659 159

N2 CuF d 61.8825 139 2.19 63

OC CuF e 75.406 150 2.31 65

a. C.J. Evans, M.C.L. Gerry, J. Chem. Phys. 112, 9363 (2000).b. J.M. Michaud, S.A. Cooke, M.C.L. Gerry, Inorg. Chem. 43, 3871 (2004).c. J.M. Michaud, M.C.L. Gerry, J. Am. Chem. Soc. 128, 7613 (2006).d. S.G. Francis, S.L. Matthews, O.K. Poleshchuk, N.R. Walker, A.C. Legon, Angew. Chem. Int. Ed. 45, 6341 (2006).e. N.R. Walker, M.C.L. Gerry, Inorg. Chem. 40, 6158 (2001).

FCu FCu - H2 H2

r(H2 Cu) = 1.52 A, r(CuF) = -0.008 A, r(HH) = +0.087 A,electric field gradient at copper increases by a factor of 3

APFD/ECP10MDF & aug-cc-pVQZ

Zinc plasma

Tin plasma

Copper plasma

r(H2 Cu) = 1.52 A, r(CuF) = -0.008 A, r(HH) = +0.087 A,electric field gradient at copper increases by a factor of 3

this talk

FC02(Grubbs)

FC03(Obenchain)

TH16(Pickett)

In other presentations in this Symposium we will talk about other complexes,ortho and para spin statistics, and our suggestions on spin-spin coupling

APFD/ECP10MDF & aug-cc-pVQZ

Acknowledgements

• Pete Pringle - sage advice & withering criticism • Steve Cooke - co-running the research group• Dan Obenchain – being a wise-guy (in both senses)• Brittany Long – adding new science• Herb Pickett – spectroscopic expertise (SPFITish) • Jens Grabow – keeping the spectrometers humming • Bob Bohn – not breaking the spectrometers• Chinh Duong, Brooke Baker, Lucas Hansen, Derek Frank,

Samantha Savitch, Tyler Holzschuh – being undergraduates

nuclear spin – nuclear spin interaction tensor

D(free H2) kHz D(H2 in H2 AgCl) kHz

Daa = -576.8 Dbb = -439.02

Dbb = +288.4 Daa = +165.6

Dcc = +288.4 Dcc = +273.42

a

b

c

a b

para-H2 CuCl63Cu35Cl 65Cu35Cl 63Cu37Cl 65Cu37Cl

(B+C)/2 /MHz 4781.8759(3)a 4740.4245(2) 4621.9139(3) 4580.1110(4)

D /kHz 2.58(4) 2.52(3) 2.44(3) 2.39(6)

eQq Cl /MHz -24.430(4) -24.428(2) -19.249(1) -19.215(6)

eQq Cu /MHz 54.057(3) 50.017(2) 54.056(2) 50.035(5)

CI Cu /kHz 12.1(2) 13.1(2) 12.1(2) 13.5(3)

rmsb /kHz 1.6 1.1 1.0 1.1Nc 30 15 14 10

a Numbers in parentheses are one standard deviation in units of the last significant figure.b Microwave rms =c N is the number of lines included in the fit

a Numbers in parentheses are one standard deviation in units of the last significant figure.b Held to the value of the ortho-H2 CuClc Microwave rms =

d N is the number of lines included in the fit

ortho-H2 CuCl63Cu35Cl

(B+C)/2 /MHz 4781.572(2)a

(B-C)/4 /MHz 4.01(2)D /kHz 2.58b

eQq Cl /MHz -24.7(1)eQq Cu /MHz 54.7(1)Daa /kHz 190(10)Dbb-Dcc /MHz -791.996CI,Cu /kHz 12.1b

rmsc /kHz 19.2Nd 11

Treating the two coupled hydrogen nuclei as one

As is well-known, H2 can be in the para, Itot = 0, or ortho, Itot = 1, states

The spin-spin splitting in the para state is zero

For the ortho state the two nuclei can either be treated as two interacting spin-1/2 nuclei or

as one combined nucleus with an effective spin of 1the results are identical

Here are two var files for Pickett’s SPCAT

ortho test 4, single I = 1 nucleus 10 1000 5 0 0.1760E-11 0.10E+07 0.1E+01 1.0'a' 3 1 0 10 0 1 1 1 0 1 1 10000 10000. 0.000 / A 20000 2000. 0.000 / B 30000 1000. 0.000 / C 110010000 45. 0.000 / 3/2 Daa 110040000 15. 0.000 / 1/4 (Dbb - Dcc)

ortho test 5, two spins of I = ½ 10 1000 5 0 0.1760E-11 0.10E+07 0.1E+01 1.0'a' 22 1 0 10 0 1 1 1 0 1 1 10000 10000. 0.000 / A 20000 2000. 0.000 / B 30000 1000. 0.000 / C 120010000 45. 0.000 / 3/2Daa 120040000 15. 0.000 / 1/4(Dbb - Dcc)

For both tests, Daa = 30 MHz, Dbb = 15 MHz, and Dcc = -45 MHz

one spin 1 two spin ½

The extra transitions in the file on the right are the para state transitions and are D independent

the two cat files

Internuclear distances from nuclear spin – nuclear spin interaction tensor

Daa(H2) = -576.8(4) kHz, Ramsey and coworkers, Phys. Rev. 87, 395 (1952)note: D = -10 d, as given in the Ramsey articleg1 = g2 = 5.5857gives r(H-H) = 0.7468 Are(H2) = 0.7414 A, r0(H2) = 0.7510 A, rs(H2) = 0.7462 A Huber and Herzberg

The nuclear spin – nuclear spin tensora notation recommendation

Hss = IiDijIj where D is traceless

Hss = 3SaaIiaIj

a + 3SbbIibIj

b + 3SccIicIj

c where S is not necessarily traceless

when only one component of S is fit, Daa = 2Saa

when two components of S are fitDaa = 2Saa - Sbb

Dbb = 2Sbb - Saa

Dcc = -Saa - Sbb

when all three components of S are givenDaa = 3Saa - (Saa + Sbb + Scc)Dbb = 3Sbb - (Saa + Sbb + Scc)Dcc = 3Scc - (Saa + Sbb + Scc)

We recommend, to avoid confusion, that D be fit and presented